Some people find 2.5.0.8 a bit buggy depending on your setup. Many run it without problems. Either way I would not delete your 2.1 folder unless space is a real problem. Deleting should not cause any problem with your 2.5 install.
Another consideration is that there are more sequences available for 2.1 from which you can borrow. See http://www.landolights.com/main/component/option,com_remository/Itemid,54/
will I be able to move the sequence from 2.5.0.8 over to 2.1?