Noah Smith has an interesting post, “If you get a PhD, get an economics PhD.” While I agree with most of it, I think he is wrong about biology PhDs when he writes:
Lab science PhDs. These include biology, chemistry, neuroscience, electrical engineering, etc. These are PhDs you do because you’re either a suicidal fool or an incomprehensible sociopath. They mainly involve utterly brutal hours slaving away in a laboratory on someone else’s project for your entire late 20s, followed by years of postdoc hell for your early 30s, with a low percentage chance of a tenure-track faculty position. To find out what these PhD programs are like, read this blog post. If you are considering getting a lab science PhD, please immediately hit yourself in the face with a brick. Now you know what it’s like.
While there are some labs where students are treated as cheap labor from the get-go, the problem is that many biology PhDs actually enjoy graduate school–many of us did have considerable intellectual freedom. I liked it, and in many cases, it’s a rather nurturing environment. Grad school isn’t the problem–it’s the trajectory after graduate school that’s problematic. In sense, this makes things worse: undergraduates typically talk to graduate students, many of whom are pretty happy. What they need to do is talk to the post-docs, but that usually doesn’t happen (and when it does, post-docs often won’t give you the honest skinny). The job insecurity and relatively low incomes compared to economics PhDs in your late 20s and 30s are pretty lousy.
Though your mileage may vary.
Related: Here’s a somewhat different view of econ PhDs.