Coatings differ greatly from traditional waxes and sealants. They area a class of reactive silanes/silazanes that, upon reaction, bond to each other and to the paint surface for form a matrix of Si-O, which becomes the new functional surface of your vehicles paint. The Si-O bond and the bond to the paint is a covalent bond, that is, it is quite permanent as opposed most sealant that form a hydrogen bond to the paint. Though other reactive chemistry and resin carriers are used, the ones about are the most common.

Coatings range from semi-permanent to permanent. If properly prepped and maintained, they will last anywhere from 2 years to 11 years (I can't really say longer as there are no vehicles I am aware of with a paint coating being on longer than 11 years) but I don't expect that coating to fall off the car at this point. One important thing to consider is that, if you always want your car swirl free, you will be polishing it in the next 2-3 years to remove swirls that have developed from normal use, and in the process, you would remove the coating. That is not to say you can't get more than 3 years without damage, but generally, a daily driven car lives in the real world and much of the potential damage to the paint is out of the owner's control. So the question becomes, does a coating that lasts longer than 2-3 years provide much benefit beyond that 3 years?

Coatings offer many benefits that cannot currently be realized with the available sealant offerings, but there is a catch there, I'll explain. Most coatings on the market recommend a silica based topper be used. The very high silica content of premium coatings is susceptible to water spots from hard water, to alleviate this, a topper is used with a lower silica content. This topper offers many of the same benefits with the exception of the hardness of the high silica content, now your topper is the functional surface. So you can get nearly all the benefits of a coating from just the topper, the exception is the hardness.

The hardness of coatings is greatly overplayed. You'll see many listed as having a hardness of 9H, and many people associate this with the Mohs scale of hardness and the inclination is to assume this hardness has a direct relation to scratch resistance. One brand has capitalized on this and even has an offering called Mohs and Mohs+. The thing is, the 9H referenced is actually based on the pencil hardness test, which is a very common method for testing all sorts of coatings. The 9H pencil is a mixture of hardened clay and graphite (definitely not the diamond of the Moh's scale). In reality, most coatings are about 4-6 on the Mohs scale. Depending on your paint, coatings may be much harder or only a little harder. Most german paint is very hard, with a few exception, while japanese paints are very soft; american cars are somewhere in the middle. The hardness of a coating is much more valuable on a japanese car than a german car. Considering that your car is being blasted with sand (quartz, mohs 7) all the time, the hardness is not all it's cracked up to be IMO. Certainly if the aluminum oxide in polishes can remove a coating, so will the steel wheel of a lighter, or a key, or the sand on the road. Based on my testing I've found that the hardness has little to do with scratch resistance, it is more the slickness of the surface that help resist damage.

Coating do have other benefits as well. They release contaminant much easier that a sealant (anti-fouling), so you are less likely to put swirls in your paint as a result of you wash and dry techniques. They also hold their gloss better than wax or sealant so a coated car will look nearly the same a year later as it did when it was coated. Coating are also extremely hydrophobic, which makes for great pictures of water beads, but they also sheet water very well. This sheeting combined with the anti-fouling means that after a rain, your car will look really good even without a wash.

Coatings are also lower maintenance. obviously they don't need to be applied frequently, but the anti-fouling properties means that washing is easier as well. You should, however, reapply the topper every 4-6 months.

Coatings offer a unique glassy look that can't be achieved with waxes or sealants. FINALLY A SHORT THOUGHT!!!

Coatings have an actual thickness to them and since they become the functional surface, they also take the swirls and scratches. when you need to polish to remove scratches and swirls, you are removing less clearcoat in the process. This is a huge advantage if you want to polish frequently, but don't want to respray the car eventually due to thinning clearcoat.

Coatings are generally more chemical resistant than sealants and waxes. Waxes can be stripped easily by most strong chemicals. Sealants are more resistance, but tend to strip if exposed to stronger acids. Coatings fair very well against most chemicals. That's not to say that you should intentionally spray your vehicle when wheel acid or engine degreaser. Those strong chemicals can degrade your coating with frequent use or long dwell times, but generally your vehicle will be well protected against the occasional contact with a strong chemical.

The downside to coatings are their cost and the prep work. Coatings need to bond to the paint, so there cannot be any polishing oils or old wax/sealant on the paint. This is usually removed by polishing and/or with a body prep solvent. Since coatings will be on the paint for several years, its important to remove as many swirls and scratches as possible or they will be visible through the coating, So instead of a 20 minute wax job, a coating process will take many hours. They have to be leveled as you are working or you will get high spots that must be polished off, so installation can be tricky. They will lose their hydrophobic characteristics over time, that does not mean the coating is gone, it's just lost some of it's benefits. This can be resolved by adding a topper or sometimes a strong decontamination can bring the beading and sheeting back.

Coatings do require maintenance, as mentioned. They should be decontaminated every 6 months and a topper applied to maintain the hydrophobic and anti-fouling properties. They are NOT a license to neglect your paint. If you neglect them, they will fail like anything else.

Finally, with regard to warranties, read them carefully. I have yet to see a warranty that is better than what you would get at a dealer, period. There is an exclusion for scratches, swirls, marring, scuffs, scrapes and chips. There is an exclusion for damage from automatic car washes, incorrect wash techniques, brushes and contaminated wash tools. There is a exclusion for neglect or carelessness as well. The vehicle must be brought to an installer yearly for inspection and maintenance. So if you have a bird bomb or water spot, the coating should be able to withstand that for a little while. If you end up with an etching from those, then you waited too long and were 'careless or negligent'. See where I'm going? You are not paying for a superior warranty, you are paying for a superior product, but you need to care for it like anything else. Some warranties cover flaking and bubbles, I've never seen any coating do that and I doubt it's even possible, so it's a good warranty, but no different than if I told you that I warranty the pigs I sold you will not fly.

The coating market is ever expanding, but below are a few recommendations and a little information on their properties, note that this is limited to consumer grade offering as several of these products listed below have a Pro-only offering that is only available to authorized installers..

Pinnacle Black Label Diamond Surface Coating - Very easy to use with up to 3 years durability, most are seeing 1.5-2 years in the field. Spray on coating that is super slick but does not add any hardness.
Duragloss Enviroshield - Very Easy to use with up to 2 years of durability. Moderately slick spray on coating that does not add hardness. This is a very economical entry into coatings.
Carpro CQuartz Classic & UK - Moderately difficult to apply, durability of 2 years with a measurable thickness and hardness.
22PLE Coatings - Moderately difficult to apply, with the exception of HPC which is fairly easy. durability of 2 years with a measurable thickness and hardness. These are very glossy.
Gtechniq - Moderately difficult to apply, durability of 2 years with a measurable thickness and hardness. Their EXO coating is very glossy and slick.