I don't really know the ins and outs, but you can still datalog, but just not for as long. The Kpro V4 has a faster chip, has flex fuel and bluetooth, it also has some protection parameters like lean situations, overboost, low oil pressure etc, but that'll all come with the cost of adding extra sensors I imagine like most other standalone units.
Like I said, unless you're looking to add loads of protection, datalog quite a bit or run different fuels, its not much I would worry about. You could always sell the Kpro and go for a k100 if you're not really interested in anything other than a good map. Most people won't need anything the Kpro V4 has to offer really.