By far.

definitely displays more tact and cleverness than tiana, who makes numerous stupid decisions

Belle looks very young but Tiana looks old :/

I never consider Belle is smart while Tiana is when she refuses Dr Facilier's temptation and later uses her advantage as a frog to defeat him.

I think it's obvious.

Both of them do a lot of stupid things, but Tiana has lots of knowledge with regards to food and business, despite likely not having an education and is incredibly quick on a feet (also, the things 3xZ said as well as the fact that she reads the newspaper showing us that she actually wants to learn about what's happening in the world). Belle just reads, has little to no foresight, and pretty much the only example people give of her being smart is that she lies to Gaston to get him out of her house (they usually change it to her "tricking" him).

I think Belle displays a lot more common sense than Tiana. She's also quick-witted in regards to how she reacts and responds to Gaston.

Belle doesn't really *do* anything stupid - with the exception of going to the West Wing which was forbade, but I don't see that as a mark of unintelligence. I think, while Tiana is smart in some ways, her not realising/putting together in her mind that the fake Naveen was marrying Lottie even AFTER she had found out that a fake Naveen was running around is just... stupid to the extreme. I mean the thought didn't even occur to her. Belle would at least put two and two together- she definitely wouldn't be as silly in a situation like that.

By a long shot.

Belle is so smarter:-)