I have an HTC One Mini. It’s pretty good (so far) – not as big as some “phablets” like the HTC One or Galaxy S4, but bigger than an iPhone or my old Motorola Defy.
The only downside that I’ve found so far is that a) it’s “monoblock” construction – that is to say you can’t get into it, so if the battery goes down the pan or anything else of that nature, it’s fubarred; and b)it can’t be voice controlled which is a pain in the car.
Stick with the Android operating system if you can. I don’t know anybody who has anything good to say about iOS ro Windows Mobile.