Comment below rating threshold, click here to show it.
Neither Mundo nor Udyr contribute much to team fights. At best, Mundo does average DPS and good tanking, provided the enemy team is dumb enough to focus him instead of Corki. And unless Undyr gets fed (and how in the hell is that going to happen?), he just feeds in the 5 man gank squad.
But they push lanes and drop towers very well. They are the most valuable when the other 4 defend and they push an unattended lane.
You don't want your traditional carries solo pushing a lane because they die if they get stunned. Corki, Tristana and Tryndamere can almost do it with their evasion but and Tryn also has hit ult but they're still one stun, one flash away from death. To be a good pusher you need decent DPS, great minion killing, good tanking and good movement speed. And lots of sight wards in the jungle.
Udyr is more versatile but less reliable. If he gets fed, he can do OK DPS, OK tanking, OK pushing and OK CC. While he doesn't excel in any of these, being able to switch his function to meet the need is powerful. Problem is, he's so easy to shut down early game that he rarely gets the XP and gold he needs. He's a feeder from level 1-8.
Mundo is less versatile but more reliable. He's naturally strong and doesn't require any serious feeding to be a good tank/DPS. But that's all he's got. He'll always be a tertiary target and he'll have too hard of a time chasing to do much real killing.