I wan´t a bit hevier bullet in my rifle, Rem 22/250, and I was wondering witch one of thees two are a better choice for 75 grs bullet if I get a new barrel.

Think hard about the 6mm/250. Just a straighforward neck up of the 22/250 case. Same shoulder angle and position as the standard case. I find that it dramatically outperforms my 22/250. My wife's rifle has a 1:10 twist, and she normally shoots bullets in the 65 to 75 gr weight range (approx 3300 to 3500 fps). Easy to load for, superb accuracy, and standard dies from Redding.

If you're rebarrelling anyway, why not stay with 22-250 in a faster twist barrel? You already have the dies, brass, etc...

Redial

I just rebarreled my 22-250 and went with a 26" barrel with 1-9 twist. I wanted to shoot the 60 & 69 grn bullets for varmints. This twist will shoot the 50 & 55 grn bullets OK if you don't push them to fast. I tried some Hornady SPSX 55grn from this fast twist and they would come apart about 20 yds past the barrel. I was pushing them too fast and was stripping the thin skin off of them. This barrel shoots the Sierra 60grn HP better than any bullet I have ever shot. The 69grn is not far behind it. I have thought about trying some 75grn bullets but the 60grn shoots so good, just don't want to mess with it.
On another note, I had a 6-250 and it was great. Where it would shine was in the wind while shooting Prairie Dogs. It was good for those 300-400 yd shots when the wind was pushing my .223 and 22-250 around. My nephew took a small whitetail with the 6-250 from a ground blind at 150yd. It put the deer down almost on the spot w/a 100grn Hornady BTSP. Sold the rifle to finance the barrel and work on my 22-250.
Good luck with your rebarrel job.
Mike