I'll touch on the biology major decision since I covered the med side in the other thread (ask for clarification if you need it).
Despite biology majors being the rivals of the biochem majors (me!), I'll give some perspectives.
From the USAFA view: biology is often the route where biochem majors who couldn't hack orgo ended up. Probably around 20-30% of biology majors were these people. Biology is one of the largest majors (by people). This has advantages and disadvantages - more people can be "top ten percent" bio majors.....but there's a lot more to compete against! It is considered one of the easier majors at USAFA, perhaps one of the easiest technical majors (though I consider all the basic sciences to be fuzzy techies!).
Away from the negative sounding side, here's the more important part. Most bio majors loved their major, and for great reason. I loved taking bio classes as part of my major because the faculty was fantastic. They loved their teachers. They were a quirky, honest, light-hearted bunch! My scholarship adviser was the bio department head (Col Putnam) who was a blast to meet with (and incredibly intelligent). The bio dept shares the CTEF building with Chemistry. It is a nice facility with modern labs, ample practical experience, and a good environment. So, as a major, it is one to enjoy.
From a med school perspective. Biology and biochem (but esp biology) are the "standard" majors for med school. Now-a-days, that's not such a great thing, med schools like academic diversity, so a biology major doesn't stand out from the major perspective (USAFA does though!)
On the plus side: with the exception of calc 3 and organic chem, the biology major has all the med school requirements in it. Only requires 3 more classes (calc 3, replace "baby orgo" with chem dept orgo 1 and 2 along with orgo lab 1). It preps you well for the bio section of the MCAT. Of the USAFA grads in 2010 at med school, I believe 60% were bio majors.
Now, I will say, the people who did the best on the MCATs were Biochem (2 highest scores of 37S and 32T were biochem majors), only 1 biochem went to a DO school (2 bios went to a DO school), no biochem majors did not go who tried to (slight exception, I dropped for a grad program, another person dropper herself out to spend more time prepping for MCATs).
I think I covered most things there! Biology would be a good choice if you choose that at USAFA!