If you are comparing 10x42 to 10x50 the 10x50 in general is going to allow more light in to the lens so they will be slightly better in low light conditions. The 10x50 will have a slightly smaller field of view. Not sure why you couldn’t get the vortex to close down to fit your eyes, my 10x42s have plenty of movement in both directions and the 10x50s in the same model are close to the same size. Maybe try a different brand.

In the end what are you going to be using them for? Glassing mountain tops across the valley for elk or looking through timber for elk. There is a ton of reading out there on the subject on the best size binos for certain uses.