Poa annua- likes; does better in shade and wet areas. Dislikes: Heat, Cold and prone to disease. There is more, but that is the basics. Nobody purchases poa seed for greens.
Bentgrass - likes: sun, heat, cold. Dislikes: shade and poor draining areas. Can handle more stress has less diseases and new varieties are well suited for golf courses. The new varieties are far better than the old ones. Breading work is done on bent, not poa.
Ok, bent is better - why do we have poa? Poa is very good at moving into environments that bent does not do well in. It produces lots of seeds at green height (another issue with why poa is bad for golfers and ball roll), bent does not seed (at green height).
Many courses are now converting older greens to bent. They have to first address the two pit falls of bent - shade and drainage. At Biltmore we have addressed the drainage issue, but not entirely the shade issue. We work towards bentgrass, but sometimes you just need to start fresh and when you do the results are dramatic.
The next time someone says - whats the big deal between poa and bent take a look at #10 or #13 green and compare it to the others, there is a BIG difference.