The 45's are 23.2 " in diameter and 1 lb lighter but only .1" narrower tread and .3" narrower sidewall so might handle better than the 50s which are 24" tall as well but that would be more on dry pavement, on wet, slippery, cold, etc...a bit more compliance in the tires is usually a good thing.
I am on the fence about which one to go with, I have spent a huge amount of my time on cars, bikes, etc...reducing weight and it has paid off but 1 lb per corner is not a big deal.
One thing I like about this tire is the tread wrap into the sidewall, it will give more grip in snow and mud that tires without it, why offroad, etc tires have a lot of it.
Note: If you ever get stuck try dropping the air in the tires down to 20PSI or even lower and see how much more grip you get, best to not go far on that pressure though.