The galactic centre has much higher planet density. Going to one of the corners defeats hte purpose and you might as well stay at home.
But don't you think other players will at least occasionally look at the galactic center? And when they see it being colonized, don't you think they'll send colonies as well? It's basically a prisoner's dilemma. If only we move for the core, we'll prosper. But if that incites a broader race to the core, we gain very little. I believe the probability of such a race is fairly high given the obviousness of the core, and the appeal of many close planets.
The other quadrants are less likely to draw attention. Moreover, being larger, the probability of conflict erupting over a strategic region declines. Thus, the probability of us finding a dominant strategy seems higher in other quadrants. Plus, other quadrants will gradually "spawn" with new players... who we can poach, gaining strength at a greater rate. While new players appear, we can eat them one by one. I doubt the core will ever spawn players, so won't have that advantage.
