Timon and Pumbaa are among my biggest gripes with SP. Them losing Kiara all the time just feels off; after all, the two did raise Simba. Their bickering feels off, since we never saw them bicker at all in TLK (I know friends do fight sometimes, but this was a bit much). And their overly-dramatic crying feels off as well, since they shared a fair amount of emotional scenes with Simba at the end of TLK and didn't turn into blubbering masses. And it really is a shame that their jokes are more miss than hit this time around.
I think the two should have been watching Kiara in the beginning, complete with the "babysitting" joke, because that one was pretty good. But Kiara escaping from them should have been handled better, so that T&P didn't look downright incompetent at cubsitting.
I also think T&P should have been used for the rhino scene, since it's pretty fun and comedic anyway. Assuming we cut out most of their other scenes, the rhino scene seems like it would give the two some spotlight without overstaying their welcome.
As to my vote, "When the going gets tough" easily takes it. The Outsiders are in the midst of a war. I don't care how bad Pumbaa's farts are, why would they run screaming from the threat of a fart?