Who would think that you could get a serious Anime from either story lines, but somehow the people who came up with the idea for both made it work. There is humor built into the story line too and it is very enjoyable despite the corniness.
They are similar in the fact of having a cute shy main character who ends up in the center of a big competition.
The comedy is fairly similar.
The "weak" protagonist (really, it's just that everyone else is too strong) is often subjected to physical punishment. In Baka Test it's getting his butt handed to him in summoning fights and by tsunderes, while in Ben-To he gets his ass kicked plain and simple... over food. (Don't worry though, they both overcome their underdog status in their own way)
They also both have a sort-of stalker who's weak to romace cliches. A male in BakaTest, a female in Ben-To. Also, they're also both poor, starving students.
The difference is the protagonist of Ben-To isn't "the dumbest idiot around".
Yoshii Akihisa (Baka to Test to Shoukanjuu) and You Satou (Ben-to) Have the same Voice Actors (Hiro Shimono)
Both shows fight for one thing that isn't normally fought about (Grades and Half-priced food)
Both have the same Ecchi-like comedy style
The randomness, the action and the comedy go hand in hand with these two shows.
If you like one of them you'll probably like the other
The basic concept around these two shows are competition, where students mostly fight to meet their expectations. The main characters in here participates these events either by team or a free-for-all battle in a surreal battle sequence. The fighting can be absurd, but it was entertaining and satisfying, so expect some action, teamwork, and romance in here.
Baka and Test, tells a boy who helps his friends trying to reach up the higher class by competing a unique RPG battle system. Ben-to follows a boy who is caught up in all out brawl between customers competing for half-price ben-to.
Baka's an over-the-top school scenario with lots of randomness mixed in with the fighting. Baka's humor and action carries it through and makes it enjoyable. you'll find many similarities, from humor style to voice actors, but baka definitely proves itself worthy in its own right.
Both shows share premises that are very, very unique. In Baka to Test you can summon creatures that battle for you, but in Ben-To, you have different factions fighting over, well, bentos. Furthermore, in both shows, you have people who you would never expect to be friends to come together for a common cause. The humor is also very similar in both shows in that they are very cheesy. If you enjoyed either show I would take a moment to check out the other recommendation.