Not the least of which would be how many would be involved in the split.
I was part of a 1:3 split, and was quite concerned with the number of eggs we would get. For our 1st fresh cycle we got 5 eggs, which was quite disappointing. Still I tried to hang on to the thought that it only takes 1 egg to have a baby. 4 of the eggs fertilized but the resulting embryos weren't great. We ended transferring 2 on day 3, and we got a BFN. On that split I was in place number 3 of the split.
Within a few weeks, we were matched again and got started. Again a 1:3 split, but this time I was the 1st recipient. 10 eggs were retrieved from this ED, so there were not enough eggs for the 3rd recipient to get any eggs, so she was dropped from the split. Again, we ended up with 5 eggs. Again 4 fertilized but this time we ended up with 2 great looking blasts. We transferred 1 on day 5, the other was frozen on day 6. We ended up with a BFP and I'm not 24 weeks pregnant. So while I was really concerned about not having some of the large numbers of eggs that some women get (especially with cycles that are not shared), things worked out well.
So if you can, try not to worry about the number of eggs that you may or may not get. Just pray that those eggs that you get are good quality, and hopefully you'll be able to look at the ED's history to figure out if she's likely to produce good healthy eggs for you.
All the best in your journey to your family!