Key differences include the fact that all creatures and spells can act as mana producers, creatures cannot block attacking creatures without having the blocker ability, and that creatures only have one power statistic
This makes it difficult for players to get through their deck efficiently, as many basic Pokmon are crucial search and draw cards
This seems really scary in Commander, though, if you had a deck that could abuse the effect and cause the card to ETB often enough
Note: either connector can be plugged into either socket
Reid Duke has toyed with this concept as well, and Chris VanMeter, who was my original inspiration for exploring the shell, played the following version of it in this Versus video
Getting an accessible, zero-mana card draw trigger on a 3/3 for just two mana is an incredible rate by any standards