For Dungeons~
Rifle.
But then I use rifle for almost everything.
In my opinion, direct damage is going to be better for your damage output than condition damage will be. Condition damage can cap, things can be immune to it, etc. No one is immune to a rifle in the face. No one.
It depends what you like and what build you’re running. If you like 1v1 crowd control then go for rifle, if you like stacking conditions then go for pistol/pistol. It also depends if you like kits, but that goes down to preference as well.
With my build I find that because I run with grenade kit and bomb kit, I don’t really find the riffle all that good. Traits enable explosives to do more damage, grenades have better range, bombs give close range heals, and I really hate the rifle skills past the first two. Plus, I already have crowd control with a chill on my grenades and a immobilize/cripple on my bombs. With how much aggro I draw using those kits I don’t stay in one spot anyway, so more 1v1 crowd control is wasted.
I do however like how I can stack conditions with my pistol (I don’t use #1 only #2 and #3) when everything else is on cooldown, and I love the combo blast finisher shield #4 gives you.
Run pistol/shield if you run bomb kit. Bomb kit has two combo fields and only one combo blast finisher, with shield #4 you can make that up.
All in all, I have to say that I find mainhand weapons really lackluster and bad on the engineer. When I use them I feel like a ranger using greatsword, that is to say a class using a weapon set that isn’t fun or satisfying. Its a shame we don’t get better skills on these as we’re stuck with rifle/pistols/shield. If I could ever replace my mainhand weapon with a kit and take on another utility skill I would do so in a heartbeat.