Myself if you have the choice , go with a 54 over the 50 .
Rifling , round bottom . IMO experience it fouls a lot less , cleans easier and in most cases will group a round ball much better then folks can shoot .
As to if to go with a match grade barrel or not . IMO a good barrel is a good barrel . You purchase one from a quality maker and you wont be sorry
Match grade means the accepted tolerances are much closer and more consistent normally this depending on maker can be found to be no less the .0005 down to .0002
Also the bore will be highly polished so has to have not even light scratches either in the lands or groves . .
Does this make a difference ? Ya it can if your shooting for POI that is measured in 32ths or long distance shooting
Past that , if your going to be using this gun for hunting or trail walk / standard rendezvous shooting .
My take is there is no need for this .
I think to often with muzzleloading barrels match grade is really nothing more then a barrel that has been lapped and cleaned up so as to ensure no sharp edges .
Back in the old days it also meant no run out but with today’s tooling , that’s really minimized anyway .
I would seriously doubt that if you compared a matched grade barrel and a standard barrel of proper quality and make , that’s had a good load worked up through it , the average person would see any real difference.
Now I know some will disagree with that but the proof is in the pudding . When you get you clock cleaned on the range by a fell shooting an old CVA with a Jukar barrel and your standing there like penny waiting for change with a high end custom gun with a 250-400 match grade barrel .
You have to ask if the extra 200 was worth it .
but if at the same time , a near perfict , barrel that needs little to no break in is what your after then match grade is what you want