The 10mm has more terminal energy.
There is a thread in the hunting forum about an Oregon man that killed a black bear with a .45acp. The round will do the job, it just depends on how you feel about it.
I'm surprised you ran into a cougar in Seattle. But then again I ran into a 3x3 blacktail in a park right next to Boeing's Everett plant so I guess not real surprising.
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