I have been doing a lot of research on the Seychelles, and while I haven't been there yet, I'll take a stab at answering this question. It seems to me that there are many islands to see in the Seychelles with different scenery and experiences....like hiking, the giant tortoises, etc. Whereas one island in the Maldives is pretty much like another unless you want to compare dive sites.

I've been thinking that staying on Mahe is a good thing because it is the main island with many different options for day trips...many private boats, or group tours using the ferry system, or private tours using the ferry system, or helicopter companies....all based on Mahe. Which is still a very pretty island that happens to be accessible to everything. Including the airport.

If money was no object, we would stay at North Island and just have the helicopters come from Mahe to take us wherever we wanted to go. All private charter, of course. :-)