The Cadet is a Warrior but a Warrior is not a Cadet. The Cadet has the same Cherokee airframe as all the others with the long tapered wing with the 160HP lycoming, the only visible diference from outside is that it only has 2 side windows, all the other cherokees have 3. It doesn't make much difference, also think the back seats in the Cadet are optional, we use them here but you won't always find Cadets with a rear seat.
The Arrow is a beast, not the best flying plane. It holds alot of fuel, more than you'd expect for a 200HP engine. If you do your SE add part 141 you'll do some time in the Arrow. If you do the SE part 61 then it's all Cadet time. The Arrow is mostly flown in the CFI course because it's a complex airplane (Constant Speed prop, Flaps, Gear yadda yadda...) Personally I like the Cadets, you fly it so much that you'll become really comfortable with it, and on those solo cross countries you have plenty of room.