Don't get an Iphone if your on At&t at all costs. I'm assuming you're american meaning the Iphone is available for At&t only unless you do some hacking of your own. At&t's networks fail and can't handle the load of all the people using iphones on their networks, its documented and the company themselves admitted that its too much for them to handle. So if you want a really played out phone with shitty network connection/speeds then i'd go for the iphone. What you haven't specified that would make looking easier is are you buying on a contract or what, or are you going for unlocked GSM phones or something? Since you're considering a mytouch i'm guessing you're a tmobile customer?
I've got an unlocked nokia n78 from amazon and i use it on tmobile and i have to say it fucking rocks. Its so damn useful. Takes really good videos and pretty decent pictures with a 3.2 meg camera. the keyboard is funky but you get used to it. Its a good music phone and comes with a 3.5mm jack. And my most favorite feature of the phone is being able to use it as an FM transmitter, i don't need to burn CD's anymore, i just load some shit into my phone's library, press play and turn on my transmitter and off i go in my car with the latest music without the stupid fucking problems of fishing around for cd's