Nunu is a liability to his team until the 50 minute mark. Up until that point, he has an abysmal win rate that spans from 30% at the 15 minute mark up to 45% at 25 minutes, and increases ever so slowly until he finally becomes good well after most games will have already ended.
Udyr is bad. His win rate scales up from 45% early game and very briefly breaks 50% at the 40-45 minute mark before falling off like a brick post 50. But with Nunu performing worse over a longer period of the game, Udyr is definitely preferable.
https://www.leagueofgraphs.com/champions/stats/udyr
https://www.leagueofgraphs.com/champions/stats/nunu
I honest to god don't know why you're so butthurt about me saying "your former main is in fact not the worst jungler in the game, but is rather the second worst". Because this doesn't detract from your main point at all. Udyr is awful and sad and needs a rework.
######Oh, and by the way, op.gg only shows stats for champions if they have 2000 games compiled for them. Udyr is just under this threshold, just like Nunu and Skarner managed to scrape just above it. Their RNG polling system just got a few extra Nunu/Skarner games and a few less Udyr games this patch, but it doesn't mean that there is literally no data on Udyr.