[Styrak]

Blowback pistols are much more realistic, since they emulate what a real pistol does.

A lot of non-blowbacks are CO2 powered and might be too hot if your playing indoor.
There are some guns like the TM MK23 are propane powered and non-blowback, and that's a nice gun and indoor capable.

However most people prefer blowbacks for the nice cycling action.