I don't have too much experience with coil shocks TBH since all my FS bikes have been in the 'Trail' category, mostly.
But I'll have my 0.02p to add on the air shocks in general.
1. They are not all the same. And with every year manufacturers release better and better models like Monarch Pluc (RC3), or even CCDB Air (never used this though).
2. Horses for courses. Obvious statement but IMO using a coil suspension on a 5 inch travel bike is close to nonsense. It's heavier, bobs more (whatever suspension linkage you have) and generally gives a different feel. This feel is more than welcome on 6 inch plus bikes (AM territory etc) but do you really need this on milder trails? I probably don't. A good air shock can do very well for XC-Trail, have decent (not 100% perfect but still) small bump compliance and bottom out resistance etc. Speaking of which, another imporant factor is...
3. Linkage itself. It always amazes me how people start talking about a shock on a frame. A shock itself means little if you don't take the linkage into account. They are very very related. Shock has its own spring characteristic (ratio of force you apply to it to the travel it makes), and suspension linkage has its own leverage ratio (how the shock movement corresponds to the wheel movement). It does change a lot.
- HL Turner Spot. The stock 5.1 rockers are designed around a linear coil shock and do not work very well with small chamber air shocks. The travel feels harsh and shallow, very hard to get decent travel out of it with normal sag. However, if you put a later 5.5 rockers on this bike, the same shock feels considerably better - it's like that, really. I was amazed when I did this back in 2009 and started suspecting that shock it not everything.
- Marin Mount Vision around 2008-2009. Why they would put standard volume chamber air shocks on cheaper models (like East Peak) is beyond me. This linkage has a very strong ramp up towards the end of the travel, so much so that it's impossible to get full travel even with high volume shocks. Small (standard) chamber feels bad - little travel, not plush by any means, worse than 5 Spot etc.
- DW Link Turner Spot. IMO, one of the best matches of an air shock and linkage that I've seen. Very plush yet has a good bottom out resistance once you reduce the air chamber a little bit (I am closer to 100 kg geared). Tried it with small chamber RS Monarch 3.1 - not good, harsh etc.
- Liteville 301 MK8. Small chamber Fox it not suited for this frame. Once you put a high volume chamber, the ride transforms for much better .
- Giant Trance X 2008-10. The stock air chamber is small and this is definitely the way to go. It has quite good small bump compliance yet does not blow through travel and does not bottom out when used sensibly (I was not using it not sensibly so cannot comment further.. :). I imagine what the comments would be if someone my weight would have to ride it with a high volume air chamber - blows through travel etc.
These are all from my own personal experience. So, the brief answer is - no, air shocks are not crap. Yes, in many cases whey will track worse than coil. No, you cannot comment on a shock itself, you have to account for how well it suits the particular frame - linkage, air chamber size etc (and I'm not even starting on that gazillion of shock tunes available nowdays). Yes, you need to compromise when choosing almost everything including rear shocks, and it may be sensitivity, weight, price, reliability etc.
BTW, RS Revelation Team Dual Air is one of the sweetest forks I've ever had a joy to ride. If it were a bit stiffer even at the expense of extra 200-300 grams I'd never stop using it I think... And this is an air fork.