I think it doesn't mater. If you just now ordered a shot timer, and you are going to record a years worth of dedicated practice, you are going to get better no matter which gun you choose.
HK P30 v1
HK P30 v3
HK P2000 v1
HK P2000 v3
Glock 19
Glock 26
Beretta 92 Centurion
Walther PPS
I think it doesn't mater. If you just now ordered a shot timer, and you are going to record a years worth of dedicated practice, you are going to get better no matter which gun you choose.