From a PvE solo/group perspective:
Well, having had a good crack of the whip with both, (and the other classes too) I always come back to my scoundrel and I take him down the scrapper route *pretends not to notice people gasp* as I find it a much more interesting and diverse class to play.
While gunslinger is nice and juicy on the dps, and more popular for PvP, I just don't want to spend all my time sitting behind a rock or a portable shield. If i wanted a desk job, I'd have chosen to work on the reception of the nearest starport, not in the cut and thrust lane of the smuggler!
Yes, scoundrel (scrapper) is arguably a very weak build since the devs 'balanced' it with their rather harsh nerf stick *raises an eyebrow at the devs and silently mouths 'why?'*. Loads and loads of conversations about this in the forums, but as of yet, no indication of intent to even look into it by the powers that be. That does get me down a lot :-( Especially as I don't PvP and I understand that was the main thrust behind the nerfs.
And yes, you will feel positively gimped as you watch a sentinel fly past you and cut through the same content in seconds that just took you a good few minutes to complete.
But ultimately the scoundrel scrapper feels to me like what a smuggler should. Back blast (dirty big shot gun - boom!), dirty kick (a well placed kick to the groin!), sucker punch (the first rule of fight club...), dart (sleepy time), stealth, disappearing act (sorry folks, gotta run!) all have a lot of fun factor in them for me. And you'll be amazed at the tricks you can come up with to get your opponent (PvE) on it's back.
Alas, things go wrong ... a lot! But surely, that's the life of a smuggler ;-) Once I got Guss, my solo PvE survival got much better as he's an excellent healer and not bad with a blaster to boot. He keeps me up as I try my best to manipulate the mobs and get behind them for the harder hitting attacks.
But if you do choose scoundrel (scrapper), be prepared for a lot of creative game playing, kiting around objects for the nastier elites and plenty of fancy foot work. There's no just leaping in, staying put and spaming simple rotations. And you'll need to stay pretty well geared to. I went for cybertech so that I could ensure both myself and my crew had a nice array of gear that far surpasses the same you get from world drops/armortech. And do your forum research, there are some great gems of advice out there amongst the sea of gloom and doom that'll help you have a better chance of keeping a lovely scoundrel standing.
Have fun!
