Personally, I prefer to fight with units that can tank hits, so that they're more likely able to successfully return to my nearest designated fallback point for repairs. For this reason, I tend to favor starting factories with more expensive raiders, such as Tanks or Gunships. For the same reasons, I tend to shift towards smaller striders like the Dante, Scorpion, and Funnelweb, fairly early, after, say, 5 or so minutes have passed.
However, I also like how easy it is to avoid getting targeted when my units are cloaked, so I'll often spam Phantoms for assaults, or escort my striders with an Iris.
Finally, if the game looks like it'll drag on, I'll build superweapons within my base, starting with a single Trinity before moving onto a Disco Rave Party. I'll still primarily rely upon my striders to do most of the fighting though.
