I would sign up to both. I picked Hydra in your poll because I typically run more with them and because my AM over there is a lot more helpful. However I would definitely sign up to as many networks as you can so if you find a network has an offer you want to run, you just have to login and run it and not apply at that point.
It's also smart to split test your offers, even if one has a higher payout the epc might be higher on the lower payout network. I wouldn't split test on every network with the offer to start, but have a few at least to test.