Battlefield is the place to be. This is absolutely my favorite starter, for a few simple reasons.
First of all, the platforms are your biggest friend. Is someone on a platform? Why not SH a Nair and hit them and proceed to combo a bit around? Someone is on the ground floor and is trying to approach, while you are on the platform? DTilt. It's funny how many people forget how awesome Dtilt's range is, completely blocking any attempt to approach. And I'm not done yet. The platforms also offer a great way to get around those campy characters, which you so despise. Furthermore, the stage is quite small, which is not a problem for G&W, who excels in the air. The same might not be able to be said about your opponent. Got a ground happy opponent against you? Go for battlefield!
Secondly, the ceiling is quite low, if I recall correctly. This makes Usmash even more deadly, so go for those reads, and upsmash out of dthrow (or out of shield, for that matter). Now, this might be a plus mostly, but this also brings some negative aspects with it.
Which brings me to my next point. You might want to pick this stage against every character, but as has been said before: Snake, Olimar, Marth and maybe even Fox and Pikachu might be dangerous on this stage, because of the low ceiling and their godly ceilingkilling moves or other stuff (utilt, upsmash, uairs, tippers). This doesn't exactly mean that you shouldn't pick battlefield against these, but be careful for those moves, because they won't hesitate to use it. For the rest of the cast, this stage is probably your best bet.
By the way, I only avoid this stage against Olimar. I think it's fairly manageable against the rest of the characters, but it's just personal preference.
9/10. I love it, and it's a must for every G&W player.