While you can run homebrew on 3.73, the community consensus from sites like Vita Hacks Guide is that you should use 3.73 only as a stepping stone to downgrade to 3.60 or 3.65
: Users attempting to downgrade from 3.73 to older, more permanent versions (like 3.60 or 3.65) often faced "softbricks" where the console would get stuck in a boot loop. ps vita firmware 373 download better work