Well, I think allot rests on your desire (or lack of desire) to spend money...and on whether or not the desire to shoot an air rifle is serious enough to subject yourself to what's involved with PCPs. Clearly, there are guys who hold airguns above all else, even in places like Canada. I'm not one of those people, but to each their own. So the first decisions are usually budget, PAL-rated or not, action-type (maybe the biggest decision) and then size/weight. The last item is usually a function of how it will be used, how far it might be carried, # of shots you expect to take during a session, accuracy expectations, etc. I've been shooting airguns on/off for most of my life (over 40 years) and for ME...I simply don't get enough from the experience to warrant either spending allot, OR, getting involved in compressed air/CO2. I'm continually amazed at what's out there though...almost enough to rattle that opinion I've held for so long!
For pest control, I've come to the realization, based on experience, that heavier pellets...even if moving slower...usually work better. For that reason, I sold-off my .177 stuff...even my Chinese HPA rifle in .22 that shot pretty hard...in favor of a non-PAL-rated Diana 24 in .22. I don't own a chronograph, but the 24 shoots about 425 or so according to the specs/internet reports. I've zeroed it at 25 yards using Hobby pellets and it can shoot dime-sized groups or better off a rest with no wind at that distance. Might not sound stellar, but I'm looking for minute-of-barn pigeon neck at distances no greater than that..so I'm confident it'll do what I need it to. Spring piston guns are also among the most quiet, which can't be said about gas guns of any kind. At least in the great white north where sound moderators are a huge no-no.
I almost didn't chime-in on this thread, because my own tastes are pretty pedestrian when it comes to air guns. To my way of thinking, the higher the costs go chasing accuracy/power/consistency...the more complicated and louder the guns themselves tend to get. Whenever I've been tempted by high-power PCP air guns...I imagine a super-expensive rifle+air tank+compressor/pump...beside a single-shot 22 shooting CCI Quiet-22. The latter can cost as little at $100, and while it likely wouldn't have an accuracy edge over a top-shelf PCP gun...it may be all you need for your application..and be quieter too.
Just this guy's opinion. I'm really liking my Diana 24, it's the second one I've owned over the years.