I personally am not a big fan of working at biotech firms since their main objective is to generate a lot of money as fast as they can. A position at a biotech firm doesn't allow much opportunity to learn new lab techniques (if that is what you want to do). In most places, you will learn one technique, master it, and continue doing it for as long as you are there. In a sense, it's basically like any other paying job with the exception that you are in a science environment.
Contrarily, if you are able to land a position at a research laboratory, I believe the situation might be better in terms of your med school application. You will be able to learn multiple lab protocols and show adcoms that you are interested in a certain area of research (rather than just making money). It's a definite plus over biotech firms.
But of course this is just my opinion. I could be wrong. 🙂