Flip a quarter heads for 44 ,tails for 45.
If you reload you can make either one work.
The 45 runs lower on pressure then 44 with same bullet wieght.
Probley more factory loads for 44,but there are some hot 45 too.
I have a 44 trapper that eats anything it is fed.
Win. will handle longer longer over all lenght then a Marlin.
Just my 2 cents.
Later
Wilbe Lead