[Morgan Butler] ” I think this is because it’s hard not to lose information in the blacks when encoding. “
It’s hard not to lose information from DSLR footage. If it isn’t exposed properly you can’t really push it in post. Video #1’s contrast might have been pushed too far and the shadows have lost information and are showing some nasty artifacts. Video #2 seems to be lit, shot, exposed and graded by someone who knows what compressed H264 can and can’t do.
Premiere has nothing to do with the fact how the footage was shot.