what fingers to use on right (picking) hand

Well, I've been finger picking for a couple of years - not enough to show off, but some. I've been using my thumb on the melody string and pointer and middle fingers on middle and bass strings respectively. I started using picks on all three fingers, and then went to just using a pick on my thumb, because my fingernails worked just fine on the first and mid fingers, and not so well on my thumb. Now I've noticed on a youtube someone fingerpicking using their index, middle and ring finger. I've tried it for the last couple of days and like the more similar sound that I get using just my fingernails.

What are the merits of using the thumb, first and middle finger as apposed to using first, middle and ring fingers? Will I regret it at some future date? Should I be doing one way for some pieces and another for other? And which would be which?

Thanks for your thoughts on this!

Kay