I definitely prefer
Nora. I think the "h" on the end is entirely unnecessary, but
Nora (this spelling, obviously) is one of my top favorites. The only
Norah I know of is the singer
Norah Jones, so all the others I know (of) spell it
Nora. So I always assume it's
Nora so I guess others might as well. BTW, I think
Joanna and
Nora sound lovely for sisters. :)