Both are crime solving, detective dramas. There's quite a bit of profiling in both and a lot of psychology stuff in them. Best of all, both are comedy so it's not boring.
Both dramas involve psychology of crime, i.e. profiling and they have the same kind of clever humour which makes one laugh out loud in the middle of a serious case. Both have great leads with outstanding performances.
Its about solving murder mystery cases, involving a certain professor as the main mystery-solver, and a gorgeous passionate assistant in solving crimes.
In both dramas we have as a main lead a scientist with a strange character who helps resolve cases.
First they are both crime/investigation shows, I guess TEN is darker than MR.BRAIN atmospherically but i don't think that's makes the point of liking one and not there other. Both feature Crimes/evidence that seem impossible and illogical. Both feature a back story of seemingly unreachable criminal with which the last ep revolves around. ( MR is Jap and TEN is Korean)
They're both about scientist solving mysteries in unusual ways and both of the male scientist have a cute female who works with them and clashes with them and has a subtle hint of romance.
The protagonists of both dramas have somewhat of the same feeling. The drama has to do with crime and investigating. Both protagonists goes out into the field, even though they are not meant to be. For both protagonists, there is a "sidekick", a female character that helps them and is "used" to help solve the cases they are doing. The Female characters dislike the protagonist at first but ends up warming up to them near the end. The dramas both have somewhat of the same plot. If you like one, I recommend watching the other as well.