While not the strongest offerings in the Commander series, they are an improvement over last year and have a lot of interesting build-around commanders and fun new cards, so in some sense, you should probably go with whichever deck fits your play style best, if you have to choose just one
What is the MEGA card, and who orders it
This deck should run decently and be fun to play, both with and against
Perhaps a creatureless build is a good start for a maindeck
This opens up a lot of combo potential with either destroying your opponents artifacts or doing unexpected things with your own artifacts. Its going to be easy to grow this elemental cat, potentially infinitely, and its a very unique effect thatll be hard to remove with spot removal
Crossing the Big Bridge This has me the most excited I've been for a Magic set