10X50 are not enough noticeable gain over the 10X42, the light gathering ability between the two is nil! The Viper HD 10X42 are awesome in low light conditions! Since you asked, I choose the 10X42! (grin) Yes, I've looked through them both!
I had the 10x50 hd vipers but the. Found a deal on slc hds. The knock o. The viper hd was that they had a narrow fov. I think the 10x42 have a wider fov and I don't know if you would miss the larger objective.