USB inside will allow you to buy an extension cable/bracket with which you can guide them to the outside.
(I've got two of those, one with 2, one with 4 connections.... aint that nice?)
Some peripherals do come with cables, some mobo's have 'm all, some come with less... ask / view a review before you buy...
Miditower or Fulltower?
Well, depends on who you want to impress, and/or how much room you want inside...
How many devices do you want to add later on, inside?
(My Miditower's got 2 DVD thingies, 3 Harddisks, a Floppydrive, a SoundCard, a TV card, Graphics card... and them to USB brackets... plenty o'room me thinks...)
Good Luck, Have Fun...