When the level 7 Skyhammer only drops one ammo pack for himself at spawn:
Imo, nader if you play for fun, fletcher if you play to get stuff done. Sure both have their uses (everyone else has already talked about them), but let's just admit it, nader is more fun lol
Proxy is fun too even though she's a little @$!#. But yep, I agree with most people saying Fletcher. He has assault-level killing potential and is typically considered the best engineer. There are plenty of mercs more or equally capable of fragging than Nader - even many fire supports. Nader may be considered noob friendly, but I always suggest beginners buy her later in the game. A rookie Nader contributes nothing to a team whereas a rookie Arty, Stoker, Fletcher, or whoever can at least provide some support and objective play.
Apparently we need a big fat prompt upon launching the game that states this.
Proxy is, like, literally Hitler.