"What are your opinions on them"

Folding bikes are not as good mechanically as the best full size bikes, which is why they are not used in competition. The smaller wheels make for a rougher ride, and fall more easily into holes. They are often less stable.

http://en.wikipedia.org/wiki/Folding_bike

That said, my guess is you will get a lot more use from a folding bike due to its superior practicality.