It bounces absolutely everything except for the largest sea creatures around
Technically, both cards can do the same theft effect with a small difference: The creature half can exile a card from an opponent's hand, and they pay its mana value to have Valki transform into it
The second kind of deck is more commander-centric, using prowess to try and win by commander damage a significant amount of the time
Rammas Echor, Ancient Shield Rammas Echor, Ancient Shield has something I really enjoy: it cares more about what you do rather than depending on your opponents' moves
Given Valgavoth's story in Duskmourn, being the enemy of the table at large is an absolute flavor win for the story but it's easy to call something a flavor win when you don't get knocked off the table for running it
For one mana, Arni Brokenbrow can end up doing some serious damage