I have an AT-X, AXSR & AICS AXSR chassis. This week sold my AXSA and previously owned an AT, AICS1.0 chassis... They are all good in their own ways.
The AT-X is obviously built for barricade shooting. It is a very nice rifle, mine has not yet reached it's full potential with the short NV bridge and weights but it is pretty easy to shoot. The front end is a square box tube, with an arca rail built in... It's not very comfortable to carry around the hills, compared to an AT with the rounded plastic skins. They are very bare-bones, you have to add a bag rider, rails, weights, forward sling mount etc. but this isn't a bad thing, it's a bit of a blank canvas allowing you to turn it into what you want and keep initial costs right down. You can run an 18" barrel on it, the competition trigger is nice.
The AX comes with the enclosed rail front end and 20MOA (removable) rail, if you're planning on running clip-ons or hunt with it, this rifle is a lot more comfortable to carry around and just generally shoot. I have shot the last 3 years of national PRS matches with an AXSA, Victor Company HR1 front rail, modified Area419 hand guard arca rail, thumb shelf, AR grip mod etc... Spent a tonne of money chasing what the AT-X now delivers out of the box. Like the others have said, 4,000 rounds is a GOOD thing, the rifle is run-in and slick. I'm a bit sad going from my smooth, sleek AX to a brand spanking new AT that needs a thousand rounds to get back into the groove. The AT-X is definitely a nice rifle, you'd struggle to be unhappy with it, just be realistic about how much you'll have to spend to get it going (muzzle brake, bag rider, weights etc. - if you're into that).
The AXSR is more of a hybrid blend of a magnum AX and an AT-X. Built in stepped arca rails, folding stock, enclosed front end, updated back end etc. But is clearly a long action which may be problematic, even with the 308 bolt / magazines if you're planning on turning it into a race gun 2etc. The 20MOA top rail is integrated on the AXSR, cannot be removed. I love this rifle, it is the first to come out of the safe these days. With the Proof 26" carbon 1:8" barrel in 300PRC, it strikes like lightning!
To throw a spanner in your plan, now having time on all three and other AI's, I'd consider an AXSR with a 300WM and 308Win bolt, giving you the ability to run one rifle from 22 Creedmoor up to 300PRC+.
View attachment 7768201
View attachment 7768207