This is my opinion on rear shocks, if you want to talk front, then there are more things to consider...
Fox makes great shocks, but it's all about intended use! If you are loaded down or doing a lot of fast driving I wouldn't get anything less than a 2.5" shock. If you mall crawl and hit the occasional trail or go camping but don't over load the thing than a 2.0" shock will do the business.
Remember when you buy a nicer shock like a Fox/King etc in a 2.0" size you aren't getting a better shock than say a Bilstien 2.0" 5100 shock. But you are paying a lot more money for it. Now the money isn't wasted, what you are buying is a fully rebuildable, fully adjustable shock that you can tailor in a million different ways to fit your needs. You can change compression and re-bound valving, you can change the PSI of the nitrogen, things like that. If you are looking for something that has those features, then getting a 2.0" Fox/King is the way to go. But if you want a nice bolt on 2.0" shock that you are just going to use like 95% of people do, I wouldn't waste the money.
Reservoirs are another discussion and can help bridge the gap if you are a moderate user, but don't have the funds to spend on a larger 2.5" shock. The pure advantage of the 2.5" shock is you have a lot more shock oil in the shock, which allows the shock to stay cool and work better for longer. Once the oil gets hot, the shock fades and the valving doesn't work like it should. a reservoir will give you the added oil capacity and cooling without buying the larger shock. This could be a reason to get a Fox/King type shock, or you could buy something like Bilstein makes that has a small reservoir but isn't rebuildable.
Also keep in mind Fox does not make a bolt on shock for 3rd Gens that I know of (may be wrong here).
What are your plans for use? This will help answer a lot of the questions!!!!
