What are you going to be doing? Will you simply be storing/printing/viewing photos, or are you wanting to edit them too? And what sort of photos - family snaps, or more professional photos/designs?
I'm surprised you don't like iPhoto, plus it doesn't sound like you gave it much of a go.
I've never used Picasa, but I've used plenty of other photo management apps and iPhoto beats them all. What sets iPhoto above the rest IMO is its powerful searching capabilities. If you apply comments and keywords to your photos you can use the various search methods to find photos fast. If using it for family photos, you can't beat iPhoto's slideshows for a quick and impressive gift for grandma!
Anyway, enough ranting. If you don't like it you don't like it.
I've heard good things about
iView Media Pro (21 day trial available)