Right now I'm using ipad 2 with logitech ultra slim keyboard. Not to heavy and not too light. Suam2 kuku la. The best thing is to type using keyboard with 9.7" display. Furthermore, much faster type than typical on-screen keyboard.

My suggestion, go for ipad air if you want big screen and much light than previous ipad. If have extra money, buy bluetooth keyboard. If you love with small screen better go for ipad mini 2. But what I know 64-bit processor need at least 4gb ram. I bet apple had solution for this