The LSAT is a logical reasoning exam... The MCAT is a logical reasoning/problem solving exam based on scientific knowledge. Both encompass similar test taking strategies and problem solving strategies to do well, aka they are both very similar. Except for the MCAT you need to be familiar with the scientific knowledge + the style of questions, as the LSAT you simply need to be familiar with the style of questions (hence their no prereqs for taking it).
So yes you can compare the two with each other.