I can see using same on both side for P2P, but if you're doing multipoint and need to go more than 200M you would want the larger gain on the client end. Maybe shouldn't use Mikrotik for any multipoint? That's part of what we're trying to learn.
This link is just a backup and we wanted to test multipoint operation over time. It turns out is was more reliable than I thought. One of the outages was our guys moving the radio and the other was a major storm with over 1 inch of rain per hour. Prior to that it hadn't gone down at all in 3 months, although we haven't had really heavy rains. That being said, I agree it seems 500 meters is a little too far for multipoint with Mikrotik at the moment.