Well the u1 be upgraded to 6.0 marshmellow. One feature i like is the ability to make your sd card the main install. I know you can move some stuff using appmnger 3, but this doesnt work with everything and you can still have traces (data) left behind. This can fill up the small internal drive quickly. An internal drive could be 4gig if the unit has the ability to change the main drive to sd. Sd cards are very inexpensive and fast. I have a 64 gig sd card in mine but i cant transfer everything. Some apps move and some dont well marshmellow be available or is there an app i can get that well change my internal drive to sd or usb. I know there use to be one called internal2sd but it stopped working is there anything like that out there.