Well I'm just saying who I personally have found better for fighting bosses and normal battles:
Obviously I have to use Cloud (until disk 2 when you have to use Tifa then Cid).
I use Yuffie because she has alot of attack power and if you complete the Pagoda in Disk One she can get All Creation (while I was on the Pagoda I got her Level 3 2nd Limit Break so I could easily use All Creation!).
And well I use Vincent and Cid alot I think I neglect alot of my characters I barely use Barret or Red XIII.
Well that is who I have found most useful.