Some of my own games, Howies alone pretty much do the brunt of he work... and some games, Stealth Fighters. Most of the time, both. If the AI has Vet Mech Inf, particularly on defensible terrain (or with SAMs), the Howies are really the best option if I had to choose one. If the AI has Riflemen and some Vet Alpines, Vet SFs usually get to swarm the AI (SFs can repair sooner, since they can return to an Airport city on the same turn as attacking). I also use SFs to block partisan formation, particularly on difficult terrain, en route.