I am with you 44man!
I have to think that slow twist was a carryover from .44-40 days for lightweight boolits. The .44-40 twist was slow as well. The .44 mag. Marlin was intended to shoot pistol boolits and does so reasonably well if they are not over 270 grs. or so though a faster twist would make the gun so much more versatile and not hurt accuracy with the lighter weight boolits.
Now why on earth Marlin would have saddled the .444 with such a slow twist is beyond me and most others. It was supposed to be a "modern .45-70" operating at higher pressure but they set it all up to shoot handgun boolits and lightweight handgun boolits at that. If made with 1:20" twist or thereabouts it would handle boolits of 400 grs. easily making it competitive with the .45-70. That is a different discussion though.
Longbow