I am actually considering using both. The zero-deposit offers on Haveno would not be subject to taker bots because a password is generated on the client side that must be entered before the offer can be taken which would make them immune to the bot issue you bring up. OpenMonero has a UX advantage since there is no software needed and it just runs in a browser like LocalMonero did. It seems to me the best solution is not one or the other. It's both.