1; They can teleport.
2; They can fly.
3; They are cool.
4; They have extra attacks.
5; They can create a duplicate buddy
6; Their duplicate buddy gets attacks of opportunity, which benefit from the Sentinel feat.
7; Their duplicate buddy only is destroyed at the end of their turn, allowing for shenanigans with readied action movement and/or mid-turn movement followed by a quick swap.
8; They get two duplicates at higher level
9; They are fun
10; I like them.

Thank you for coming to my TED talk.