My run down on the neutrals
If the character lacks good platform pressure, then I like BF. Characters that I like playing on BF include Captain, Ganon, Fox, and Lucario, and Ice Climbers. For everyone else, there's FD / SV. Don't fight a Diddy on this level, take him anywhere else.
FD has larger blastzones (good for us) and the lip to mess with people's recoveries. Great level for her.
SV is better against campier characters due to the size reduction, and resting the balloon is the best taunt ever. The floating platform can lead to tech chased rests, and you can uair them safely through it if it's moving away from you, provided you drift the uair away from the direction it's moving. Note: this shield pokes if they're shield is low, and sets them up in the air for further chasing.
Yoshis is good against characters with multiple jumps and PK kids, as it allows their recoveries to be intercepted much easier. The platform constantly moves, preventing it from being exploited too much, except for the likes of Snake, G&W, and Marth. Avoid them here, if you can. Work on using the wall to stage spike.
Lylat is great against characters with crap recoveries. Characters like Snake, G&W, and from my experience, Lucario, are really good on this stage. Don't take them here either.