"Even if it's not subsidized, the student plan is often much better and/or cheaper than a "market" plan because the insurance company knows that, in general, a group of students in their 20s are much less likely to have high medical bills than the open market, which includes people of all ages! "
This isn't really how it works under the ACA. Plans are priced by age groups, so even in the open market right now, you are still priced along with other people your age. A 22 year old pays a lot less than 50 year old in the current market. I would look carefully at the coverage offered by a school plan before accepting it. If it isn't sufficient for your needs, that could be a big problem if the individual market falls apart in the next couple of years (as it very well might).