Sniper 66,
I believe these have the match chamber (the difference is a match
chamber (not "barrel") -- the chamber is a tiny bit tighter than the regular chamber):
MTR
AT-One
MDT
LRP
I've had a bunch of CZ and BRNO rimfires, and still have 15, but no 457s. Nothing wrong with the 457 per se, I've looked at several of them but I just prefer the 452, 453, and BRNO guns because of the feel and the way they are built. I've read almost all posts on various CZ forums (RimfireCentral BRNO/CZ forum being the biggest with the most serious shooters), and the 457s seem to generally shoot as well as the earlier guns, but not necessarily better. Now, a big, heavy gun like the MTR is easier to shoot tight groups with, so some shooters tend to get more consistent tight groups with them. Plus, the match chamber may increase the odds of getting a great-shooting one, but it's not as if regular CZ chambers are big and sloppy or the guns won't shoot well.
One key to shooting good groups with a CZ (and probably any other rimfire) is to find ammo that works well in the individual gun. And the higher the quality of the ammo, the better it
might perform (you still have to find what works in a given gun, even if you're shooting the expensive ammo). IME, it's not uncommon to take two different loads that cost about the same, and see one of them shoot groups that are half the size of the other in a given rifle. I have a BRNO Model 4 and a CZ 453 Varmint that both shoot groups in the 0.3" range or even less at 50 yards with mid-grade target ammo (SK Pistol Match and Standard Plus), but the Model 4 shoots Pistol Match better and the 453 tends to shoot Standard Plus better. I also have several other CZs that shoot only a tenth or two larger groups than these two. But the ammo is key, and the same ammo doesn't necessarily shoot best in all of the guns. The BRNO Model 4 is a pretty big gun, and it is definitely easier to shoot consistently tight groups with.
I think I agree with d2wing; buy the gun you like best and find ammo that suits it. Most likely it'll shoot very close to the MTR, with the possible exception that the large MTR stock may be a little more conducive to helping you get your best groups. Bigger guns are just easier to shoot groups with, so if you are most serious about repeatedly shooting your best groups, you might factor that into your decision.
Model 4 with its 27" barrel is a physically large gun:
453 Varmint with 20" barrel is significantly more compact, but a solid gun:
I'd wrap up by saying that I generally prefer shooting a larger gun from the bench when shooting for groups. The two largest rimfires I have are the Model 4 above, and my Winchester 52B with Thomas trigger. They are also my favorites to shoot for groups because it's more satisfying to shoot consistently tighter groups. It may be more fun to carry a smaller, lighter gun back and forth to the range, but for actual shooting, I get more satisfaction from tighter groups.
One additional advantage to the Model 4 and 52B for me is this: I shoot on private land by myself most of the time (nobody blasting away with a centerfire or some type of handgun next to me). A .22 rimfire barrel of 27 to 28 inches like these two is very quite with standard velocity ammo. There is no need whatsoever for hearing protection, which makes my shooting experience much more enjoyable. For example, when shooting a steel target at 25 or 50 yards, the clang of the bullet hitting the steel is louder than the report from the rifle.