I have no idea which order is better, but the meat was thawed and I had to cut the onion up yet so it was about saving time for me, ha.
For me it comes down to two things:
1. Mrs. Velo likes likes the onions as inconspicuous as possible in the chili. It is interesting because she will put big hunks of onion on her hamburgers.
2. I the flavors of my chili ingredients to blend as much as possible. Getting the onion on board with the meat for as long as possible to start with helps. I actually think chili often tastes even better as leftovers because it has more time to marinate so to speak.