Yo, I picked up Wario a while ago as a back-up character hopefully I get really good soon. I played Snake a couple of times with Wario actually so I can give some input.
Most Snakes play this match-up
completely wrong. They spend way too much time camping around with grenades which only gives Wario time to charge his fart or to somehow get through to Snake. Grenades suck in that match-up! I find grenade camping Snakes to be easy but Snakes, who know the match-up are very tough to beat. Snake actually can destroy all of Warios approaches easily with utilt. Now most Snakes save their utilt to KO you but in the Wario match-up it's actually better as a regular attack.
Snakes utilt ***** all of Warios approaches. Additionally he can walk to ftilt, which is really hard to get around if he knows how to do it.
Warios best approach is either Dair or SH Bite from my experience but utilt beats both pretty easily. The only other option I can think of is a grab but a step back + ftilt will cover that option too.
Snake has a
massive advantage on the ground so unless you find a way to get him into the air you won't win. Once Snake is in the air it's not too hard to land uairs to juggle him and deal nice damage so if you get to grab him uthrow is actually a good choice. Just bait the airdodge and then you can clap him back into the air. Getting him into the air is however really difficult and you shouldn't make any mistakes when you get the chance to deal damage as you won't get too many if the Snake knows what to do.
Stages are very interesting because both characters have their share of good stages. Something to consider is that Snake is actually not bad at Rainbow Cruise ... most Snakes just suck on that stage lol. It's still in Warios favour on that stage though =P
6/4 for Snake on Battlefield and 55/45 for Snake on Halberd
Solid advantage for Wario on Brinstar but most Snakes will ban it anyways...so Rainbow Cruise and Frigate Orpheon are both good choices (around 55/45 Warios favour imo).
Overall I'd say it's 5/5...
Edit @ dmg
Dair -> Dair -> Fsmash can be escaped after the first dair =P