don't know the phones but it will depend on what widgets & sync options you have enabled. You can have a 3g toggle but if you want 3g on all the time then I would freeze some of the things I'm not bothered about that may attempt to sync, lessen the sync intervals or check them manually. This is not what we want to hear but phones are still a compromise especially when they can play media.
I would go for the phone you like best, then look at conserving battery yourself. I think screen brightness, 3g & data consuming apps that you don't really use are the main culprits but there's apps to help manage those. If rooted you might consider a clock speed & voltage changing app like setcpu, this lets you configure it's power consumption over times like when it's running high CPU, or getting low on juice, etc... just look in forums to get a general idea of what settings people are using because can cook it or it may be unstable if you use settings that are too extreme.
