Michael will be a all-round nuke in your deck. Pick him!

Micheal is useful in almost all formats.
Praxie is useful in elo and maybe extended.
Jay is a bad card.

Praxie's way overpriced, and he's really not worth it. If one star is the difference between the top of one bracket and the bottom of the next, then I would go with Jay, but otherwise with Michael.

Michael would be the best choice in general. Only card to out do him would be Cr Caelus and getting him is out of the question
Jay has nice damage but you can supplement him with Greem or go for a Falk who brings pretty nice attack manipulation especially in a mono deck.
Praxie is a bit overpriced in my opinion. I would suggest switching him with the many other useful 3 stars instead.

Between these three, i would say Michael. Praxie is expensive and better suited for elo. Jay is amazing depending on you play style and your other card in deck.

Michael > Praxie > Jay however it does depend on your play style

Micheal is the best out of them, and also the only one worth that Hefty price tag. Jay & Praxie, while good cards, are way too overpriced.

Michael - best ELO/DT useable Skeelz 5*. Best choice in my opinion

Jay - Good 4* but I personally the 7 power w/o any help is pretty weak especially with revenge needed. Probably take Dr Falkenstien (in mono) & Greem (if u know how to play w/ her) and possibly even Belgosi, Corvus, & Manfred depending on the deck.

Praxie - Overpriced and not worth it. Choose Chiara, Sandro (in mono), Lorna, Snowflake, & Andy Ld

+1 to most of the inputs above.
Just want to add that Eloxia is what makes Jay even scarier than he used to be. He's still prone to power and atk manip as well as DR, but the threat remains.