Fwiw, I would look at the LBT-style 300 gr. bullets for the .44, which have worked splendidly for me in the past. I've never shot a grizzly with them, but they penetrate unlike anything short of the Keith-style SWC but with much more weight (I'm ruling out round nose designs and trocar-style armor penetrators).
Using the S&W, mind the full-velocity loads. With handloads like these I'm talking about, you can expect a service life of around 1000 rounds before you stretch the crane out of tolerance on that design. I had a Ruger Bisley Blackhawk I cut down to 5 1/2" and Magna-Ported that would eat those rounds all day long. That Bisley grip helped the recoil tremendously, too.
My realistic choice for that environment? A 590A1 Mossberg loaded with 2 3/4" high-brass #00 buck. Multiple instantaneous hits will flat disconnect the CNS and require a complete reboot. By the time the system comes back on, hypovolemic shock has set in and, well, game over.
There's my $.02