This is one instance where it pays to have brains where everybody keeps telling yours are. There's no rules here. If your old one was comfortable try to match it as close as possible. But that's only a starting place because saddles that look alike don't sit alike.

Saddles are like shoes, you can't tell except by trying them. Even so, some feel great in the store and are nightmares after 10 minutes, others, don't feel so great immediately and end up super comfortable.