I have been using and iPad 2 running SD for the last year and have been happy with it, but I've just bought an Asus fonepad for £180 (having dipped my toe in the Android water by testing SD on my Galaxy S3). I'm intending to use the Asus as a pretty well dedicated SD tool.
The main reason for switching is because of the size of the unit......the fonepad seems smaller than the iPad mini and is a LOT smaller than the iPad 2
, which is great in a restricted cockpit area.
I tried it in the air for the first time yesterday evening and it performed well, not as quick to load or redraw the charts as the iPad but perfectly serviceable.
Within a few months I wouldn't expect there to be a lot of difference between the iPad and the Android version of the software.