Currently a 12Y reservist , thinking of going active. Should I stay 12y or go 35g . Also thinking of 37F. Any input on AIT or duty stations?

As a 37F on active duty, you will be forever stationed at the black hole that is Bragg.

I loved AIT as a 35G and I love the job. 12y's work with 35G's all the time and do similar work so the transition should be easy if you are able to get 35G. Plus on the civilian side the pay is wonderful.

Do what YOU want to do.
With that being said...
Get a good grasp of the 12Y MOS before you transition, it will help you out no matter what decision you make.
12Y you already have a basic grasp of what you'll be doing.
37F is a pretty cool MOS, but if the selection process is still the same as it was, it will be extremely physically intensive. 37F is a part of the SF community, you'll need to be/remain in top physical shape.
35G is a good MOS to get into. If you have GIS knowledge already, you will be an asset wherever you go, but you will truly be an asset for a COCOM. Having knowledge and experience in both Geospatial fields will also help you out significantly when you eventually end up in the civilian sector.