I would personally say Willpower for a stalker secondary. I find survivability wise, wp does much better than my regen (even though many of my friends swear by it) and I like the damage resistance, defence, perception and the heal that WP offers.
Plus, you can max out WP stalkers HP without even trying.
Alright... So I have been trying to think of something I liked in pvp, i have tried a psi/em Blaster but eh too squishy for my taste and no way to escape kinda annoying for me. How well does energy work? I heard WP is supper cheap but I also heard Regen is great too.. What do you guys think? Thanks ahead of time for the help!