When I researched on my current so-far successful Ironman run (got all research done before the base assault), I did it something like this...

Laser Rifle, Carapace, Heavy Laser, Plasma Rifle, Titan, Plasma Sniper, Heavy Plasma.

With how often Snipers hit for critical damage, I jumped straight to Plasma Sniper rather than doing Laser Sniper at all (I did it much later on when I had nothing else to research). I think it largely depends on what bonuses you get from capturing enemies, though. If you can capture a Sectoid (they never came up for me for some reason) then you're pretty much good to go with all Laser gear.

EDIT: Regarding the choice of weapons or armour, surely we can have both? Unless you mean what kind of item we would like, in which case I'll opt for additional armour (so Nanovest or Chitin Plating).