Polar bears are certainly bigger and probably nastier than a brown bear... but it feels rather anochronistic seeing one in the temperate Sword Coast. I understand they exist in the setting (I still remember getting mauled by one on a bridge in BG1 on the way to rescue Dynaheir) however it's... a bit jarring to see? I suggest swapping the textures, so you become a brown bear, assuming playable druids don't get access to brown bears at all.
