I have only ever heard "che" in spoken Hindi/Urdu. It may be similar to "veh" vs. "vaha" that the formal/official pronunciation is really "chaha," but I think people would look at you funny if you said it like this.
I've heard both pronunciations in Hindi. I wouldn't look into it too much. Probably just depends on region and speaker. In general lots of words in Hindi that have the ह sound seem to have the preceding vowel ambiguously between 'eh' and 'a' (शहर, रहना, ठहरना, etc.).