I've read conflicting info on this so I'm hoping someone can give me a definitive answer.
What I'd like to know is - which is the best framerate to shoot footage which needs to be delivered in both PAL and NTSC SD formats? The camera used will be a Varicam shooting DVCPRO HD and the footage itself won't have a lot of fast motion. The cameraman has a preference to shoot it at 24P but I'm wondering if this is the best choice. We will be editing on the latest version of FCP.
Any advice would be gratefully received.

A lot depends on what you are shooting. Is this a TVC, Doc, indy film, etc?

A few minutes of aerial footage / location shots for a potential news broadcast. I'm hoping that if we shoot 720 24P, it will be possible to use FCP 6 to convert to 50i and 60i without too much pain (or stuttery motion)..
Am I being optimistic here?

Welcome to the forum, James.

Your best bet would be to shoot at 30p; this would give you a happy medium to start with for making your conversions later.

Compressor 3 can make very high-quality conversions of all kinds; frame rate, speed, size NTSC-to-PAL etc. But, those high-quality settings will take a great deal of time to crunch the data.