I have been DJing for many years using vinyl and my trusty Technics SL-1210s but I am also obviously a huge fan of MiniDisc so these types of decks that are orientated towards DJ use have always been of interest to me.
Sadly I've never had the opportunity to try out either the DRE1 or one of Denon's DJ setups such as the DN-M2300R.
I think that as the Sony decks are individual I would favour these over the combined Denon units and I would assume both are similar to cd decks as far as DJing is concerned.
Having used cd decks such as the Pioneer CDJ-1000 on several occasions with great success, I still find myself sticking to vinyl as it is a much more physical, hands on affair and I feel like I'm putting on much more of a performance.
Saying that though, I would still one day like to acquire a pair of MDS-DRE1s as I think it would be fun and very unusual to be able to play a set from MiniDiscs for a change rather than recording my live sets onto them.