which option do you suggest?!

[amirpouyan]

Hi,
i have 3 top choice for my application. i was wondering whether to get an "exceptional" LOR from a assistant professor (we had many joint research and he said me several times that he is impressed by my abilities, i am sure he will write something spectacular for me) or a "good" LOR from a full professor with more publication and research which is Head of our department?! which option do you think is better for schools with rank < 50?

[TakeruK]

I'd go for the assistant professor that knows your abilities well and can write about them in detail to the admission committee.