tablets: What tablet to get?

[pc9460]

Hey what are some good suggestions for a table that I should get?
I'm looking for the following:

-Expandable memory
-7" or 10" screen
-Under $300
-Maybe an hdmi output
-Android or Windows
-decent battery life

They must be good, so a decent processor is required along with ram. I would use it mostly to surf, maybe do some online homework assignments with it so adobe flash player must work, watch videos that I download plus hook it up to my tv and look at etexts which are pdf format.

Also, Which one is better, android or windows based?