I would say go with the Adamant Crobat. I feel that Crobat is already fast enough as it is, and it needs all the power it can get with an attack-boosting nature. If it runs Adamant however, it would be outsped by Pokemon with base 115 Speed and a positive Nature, some examples are:
-Raikou
-Starmie
-Ambipom
-Azelf
-Mega Rayquaza
If you feel that outspeeding these threats are absolutely necessary, you can opt to run with the Hasty Crobat, but I would suggest you finding a Zubat with a Jolly Nature in order to not lower its defences.