With six jala. plants (three different varietals), there are many options on when to pick. Picked my first six of the season (green) last night. For making poppers, tend to prefer them green because the texture is firmer compared to red, stands up to grilling better. Also, green seems to maintain it's crunch better than red when pickled for winter use.
That being said, I prefer them red. The flavor just seems to be better balanced when ripe and this is how we like them freshly sliced on burgers and pizza. As for heat, cannot tell any discernible difference between the two.
Just seconding what those above are saying, whatever "floats your boat", its all good either way.