Always focus on soul rippers, a single one will easily take out an undefended commander (And considering how early you can get them, that's a feasible plan), and a group is nearly unstoppable against anything (Although they are vulnerable to other gunships, most people never build that).
I personally have a sweet spot for artillery, which in my opinion is a lot more cost effective than most people here seem to give them credit for. I suspect said people never micromanage them which is a bad idea since most artillery structures left to themselves will almost always prioritize pointless targets.
and why scu own ass all shown in this replay, remind me to never make spiderbots again :<
mass scu all the way