It's most likely a more powerful one, considering it is 2x as fast as the one in A6X. A7 GPU in iPhone 5s is slightly better than A6X (not 2x as fast).
Since Apple announced that they would have the A7 chip (as apposed to the A7x), I'd assume it's the same GPU. Not an issue really since they both have the same number of pixels as the ipad 4 which used a chip with a much weaker GPU.
It says on the apple website that the A7 in the new iPad Air has up to twice as fast CPU and GPU compared to the previous generation (iPad 4). I possibly think the new iPad Air might have a more powerful GPU due to this reason