I have a 16" AR-15 in 357 AR Max (ballistic equivalent to the 350L). I have pushed 200 gr loads to 2000 fps, but dropped back to around 1950 fps as a standard maximum for this bullet. Most 35 Rem published loads with 200s top out around 2100 fps to 2200 fps, but with a 24" barrel. This thread was about "short barrel stopping", so I really do not see the 35 Rem as better enough to matter if you are talking 18" and under for length.
Penetration is much more important for "stopping" than fpe. A lot of rounds get their high fpe numbers based on higher velocities. Higher velocities are not needed and carry more risk for under penetration up close in a dangerous game stopping application. The 350L with a heavy built 180 gr or 200 gr projectile has the penetration needed for up close stopping. The 350L in the AR-15 platform also has a pretty good combination of autoloading, moderate recoil and great magazine capacity. These all help with the very important capability for making rapid and well placed follow-up shots. My 200 gr 357 AR Max loads recoil a lot more than a 223/5.56, but getting back on target after a shot can be pretty quick (the red dot optic I use also helps with this).
In an AR-15 gun, the 450 and 458 are better for effectiveness of an individual shot, but unless a person intentionally trains and practices a bunch, I doubt they will do nearly as well in probability of getting multiple good hits in the charging bear scenario.
The 350L is probably more marginal with bigger game when you start talking hunting applications that include potentially longer distances.