Played here: https://itizso.itch.io/nintendo-vermin
I would say this has a very similar gameplay style to Ball, just reskinned and with a bit more difficulty. This game is essentially Whack-A-Mole, there's no beating around the bush there. I would say this is a bit more difficult than Ball, primarily because there are 4 potential places the moles can appear from (5 in Game B), while also having up to 4 moles (5 in Game B) coming upwards at the same time. This means the skill ceiling is a bit higher than Ball, meaning it could give a bit more entertainment overall, but it still does have the same very important flaw as Ball where once you reach score 100 (in both Game A and B), the speed resets, and I find that very annoying because I actually found max speed to be very challenging, as well as the rate in which is speeds up to be a lot better paced than in Ball or Flagman's Game B. There is one new flaw I found in Vermin however that wasn't present in Ball, and that is something that only happens in Game B. At certain points once you're fairly close to the 100 point threshold, the moles will actually come at such a quick pace that it is impossible to hit all the visible moles at once. The animation is only quick enough to allow you to hit 2 (maybe 3?) moles per unit the moles move, meaning if you have 3 (or 4? I wasn't keeping track) moles up, which is guaranteed to happen, then you just aren't gonna get 'em all and you're gonna get a strike no matter what.
Overall, I think that in terms of value and it's time-wasting capability (what I mainly base these ratings off of, since that is the goal of the Game & Watch line of products), I would put this in between Ball and Flagman. It has a higher difficulty spike than Ball for sure, but I really think I would take Flagman mostly because there isn't that extremely noticeable threshold where the game basically resets, meaning that challenge stays pretty much until I get bored instead of it being cut off by the threshold.
Game A and B High Scores: 100