Brown Bear are big and fight back, I would pick a bigger round.
If you only have a 444 Marlin, I would look into the heavy hard cast bullets. The 250 gr PT is a great bullet but I do not feel it is the best choice for the job you are asking.
I don't know if you're still considering the .444 Marlin, but check out Beartooth bullets website. They sell a 405 grain cast bullet, and have that bullet doing about 1800 feet/s out of a Marlin 444 according to their reloading data. When loaded with a good, heavy cast load, the .444 can be a better big bear round than it's given credit for.