If you can get to both, best place to check current offers is in the shops. On Grafton St in Dublin they are about 2 mins apart.
I recently upgraded my Meteor phone. Went into the Meteor shop and they only had 3 handsets in stock, of over 20 on display. Went to Carphone Warehouse and had my pick of a huge variety of phones.
Also Carphone Warehouse sometimes get newer phones, on Vodafone as well, quicker than the Vodafone stores!! In some cases Vodafone never even get these phones so I think it worth checking both.
I dont know about Vodafone but in my case, buying online with O2 is cheaper than in the retail store.
My opinion about phone models is :
if I want a camera Ill buy a camera . Ditto for mp3 player. I wont buy a inferior camera for over the odds when a proper camera is better value.
Also more importantly because I ve had 3 very short lived camera phones I have found camera phones have more things which can go wrong with them. Screens break easily even for the clamshell models I had. Then once the screen is broken its impossible/expensive to get your address book off the phone so you better have it backed up.
With all the bells and whistles I found I only ever use my phone for calls and sms so I bought the most reliable small phone I could find with no expensive screen to break when dropped, a nokia model which they dont seem to make any longer. But those are my criteria when looking and what I would ask for when walking into a store.