I've got 5.1.1 on CD and 5.3.1 on DVD (the official version in both cases). They are not really comparable because the DVD version offers so much more than the CD version, but I find that both work excellently. The DVD version has a couple of things that I need that the CD version lacks, including gnuplot and gcc, so during sessions that I need them, I use the DVD. From a purely physical point of view, the DVD sometimes fails to boot on my work machine (maybe 2/10 of occasions) whereas it always boots successfully at home (being the machine on which the DVD was created, as it happens). I think the engineering tolerances are so fine because of the amount squeezed into the DVD, that the reader simply fails sometimes. I think it's this kind of failure that causes some users to throw their arms into the air, panic and revert. (Why is this? If their car fails to start, do people throw it away or go and buy the old one back? People seem to have expectations of software and hardware that would be obviously unrealistc in any other context.) I do not regard either version as "better" than the other, it's just that one of them is bigger. They are both staggeringly good!
Fergus