Just about all of them will stack pellets at 10m, unless your a 565 shooter you might not know the accuracy differences between them. What sets them apart are the features and adjustments. I use an older Pardini K10 that has been superseded by the K12, the K12 has a redesigned trigger, action, and includes a internal recoil absorber. I also just repaired an older Walther LP201 but haven't chronographed it, both shot equal for me at 10m but the Walther trigger was heavier with a definitive 2 stages with less trigger adjustments. Would compile a list of all features and determine which ones you want vs the price. If I was to buy a pistol now I think I would lean towards the Walther, Pardini, Steyr, or Morini. Or if I got a hell of a deal, the Matchgun... Some pistols have direct pellet to breech vs a sliding probe, this is thought to be more accurate and also is a good visual indicator that the pistol is loaded. (Discharging an air pistol without a pellet loaded is penalized during a match, and yes it does happen with experienced shooters.). I also prefer a Morini grip over a Pardini, but it seems that no Morini grips are available for my Pardini. Walther and FWB both have more grip adjustments than most of the other makers, if that makes s difference. (Recently seen that someone broke off the rear sight assembly on a FWB P8x, so it's a bit fragile.). Picked up an older FWB80, spring piston powered and rebuilt it with seals and a spring. Even grabbed a Baikal 46m SSP, both are accurate but prefer a PCP for effortless shooting...
Older pistols that are taken care of are worthy taking a look at, parts for my Walther LP201 are rare now but seals are available. Just be aware that for ISSF competitions that the air cylinders have to be current as they have a 10yr service life. Pardini charges $70 to test and recertify each cylinder, not sure as to how the other makers handle them. Manufacture support is also important, Pardini and Walther answered me the same if not the next day. Assume that Steyr would do the same as well, to my knowledge, as they have a US presence.
CMP has an ACES postal match that is held quarterly, air rifle or air pistol.
https://thecmp.org/youth/aces-postal/