Im a hardcore Balrog player and have been playing him since the game came out.Hes a solid character but can be difficult to win with when you get to the top tiers.All groove rogs are good but top three I would say have to be C,A,N.
Balrogs tougest fights IMO would have to be:
P,S,N and K Grooves:Sagat
Any groove Cammy
Any groove Blanka
C and N Grooves ChunLi
After that its:
One of his worst matches is Athena.