As stated here already the combination of super speed with the power chomper was a nightmare as zombies. I did win twice as zombies but those were 50-40-something wins whereas once as plants we won 50-8.
Normally the main defense against chompers barring standing on raised terrain is shooting them before they can get to melee, with super speed this is much less of an option.
I played all the characters for this one and played both sides, but as noted here as well, a LOT of people team switched off zombies and had some lop-sided matches. One match where zombies did awful, we lost 50-17, I was the only one with more than a couple of vanquishes and we had a lot of zeroes. When several of your team are trying to team switch and you see them just standing around it makes it even more frustrating than it already was.
Despite the dominance of the power chomper my preferred character here is the power flower. I played her most for plants and electrician most for zombies. At least the electrician has several 'outs' when the chompers come hunting.