Well that all depens on what you want from a phone/what you use it for. Personally I would use both, and imo the XDA is probally marginaly "better" (but there is little in it) the toss up would be size and wether you want a touch screen. I would personaly got for the N80 its newer and smaller, the XDA mini S is nice but I dont like and wouldnt use the slide out keys on the XDA so would go for the newer (worth more £'s too) N80. Cant really go wrong with either really. I wouldnt be put of by people saying the N80 is slow, its a lovly phone and the one I used was just fine, you arre also in a good position with O2 as you will get one with out stupid software on.