Better that it's 10 inches since it's for teaching images and files like pdf and I prefer it to be seen a little bigger.
I rule out the nexus, I know it's a better machine but if the bq is enough I don't want to spend more money because the use it will be given will only be photos and opening files as safely as possible.
Another thing is that I would give it much more use like on a pc, but I know that won't be the case.
So I opt for the bq, now I'll tell you if you intend to connect via modem to get or not the one that has 3G
Regards.