If budget is a high priority then you might consider an Insignia Flex Elite. Great size and weight, bright screen, respectable specs, minimal lag, good battery life. I picked up an open box unit last week (~$117), have flown about 10 batteries worth and it is certainly capable. But it gets returned tomorrow.
A couple of small niggles I wasn't willing to compromise on: max 32gb sd card, I could not figure out a way to exit the Go app without rebooting the device, interface is somewhat clunky and the Go app crashed once the first time I used it. Worth a look if you can pick it up cheap.
So, I just ordered the Nvidia Shield K1. Looks to be a great buy for what you get. Plenty of overhead to run Go smoothly, HDMI out, front pointing speakers for the hearing impaired and upgradeable to Marshmallow. Seems worth the extra money to me.