I was in a similar position with these exact three frames. I’m pretty sure all are good choices with minimal differences.
Personally, I ruled out the Stanton due to the combination of very short chain stays and slacker angle seat tube – fine on the flats and downs, but something I don’t like on steep seated climbs.
Nearly pulled the trigger on the Forge a few times, but the very low bottom bracket (with 140mm fork), a review saying the Moxie was the slightly more supple of the two and several people/reviews just waxing lyrical about the hard to define, special something the Moxie frame has, sent me in that direction. Hard to speak for anyone else’s needs and preferences, but I absolutely love my Moxie.
For reference:
NBD/M/Y – Neverending Moxie Build