Pretty great 3d brawler of its era.
Hard as balls though.

Mechanically, there's quite a few things that separate it from others.
One, its charge attack system. The way they're implemented is pretty easy to under stand. Pretty nifty in many situations.
There are also attacks performed with combined inputs like Jump + Beat = a sweeping move which is really useful. I'd go as far and say it makes combat more complex than others for the time.
Some aspects of other beat em ups (mainly from the Snes era) are multiple pathways. One stage you'll be on a boat while in the flipside, you'll be in a Sega Theme park of sorts with a large Sonic statue.
There's also a shift button which is surprisingly useful for dodging enemy attacks. Just don't charge while shifting. It slows you down.

Big cons are how fucking unforgiving timeouts can be. The timer runs out so fast compared to other beat em ups. You might time out before your health drains.
Then there's the bosses while unique and cool, abuse the ever living fuck out of their super moves that give them invincibility frames. The last enemy gauntlet with the flying Grim Reapers was absolute cancer.

But yeah. Cool game. Cool playable characters with their unique quirks and such. Combat in general feels snappy and satisfying.