Impulse-bought 5 SARs: B6P, B6Pc, K2P, ST10, K2-45. Never owned/shot a CZ or clone prior to...
Have only taken two of them to the range so far, my time has been limited.
B6P compact : 99 rounds mixed Federal and WWB, one FTF on WWB (dud primer, two attempts). Sig 228 mags fit/load/fire just-about-perfect but won't hold the slide open when empty. Takes the other SAR 9mm magazines just fine, so one could carry 13+1 and have 17-round backups.
K2-45: 28 rounds mixed S&B and WWB. Recoil is unlike any other .45 I've owned (Sig220, FNP45, USP45, P97, Sistema, Ballester-Molina, 4516, G21)...fat grip + long beavertail + full size + aluminum frame = a pleasure. ParaOrd-mfg stainless mags DO NOT FIT and I didn't feel like trying to get them to work, MecGar-mfg Paras are supposed to work without issues but I haven't found any. So far, I like it other than only having one mag for it.
In comparison (to the B6Pc), the B6P has a slightly longer grip to take 17-round mags and a longer barrel/slide. K2P has a thicker, square slide with HUGE ejection port; longer grip (17rd) with different texturing, Novak-ish sights, and a rail. Same controls in the same place.
K2 manual's front cover says it is for "K2-45ACP, K2-9mm, K2-40sw and K2-10mm. ST-10 manual's front cover says it is for "ST-10 9mm, 40sw, 45ACP and 10mm models." YES PLEASE!