Hunter - yes, the nova core is noticeably lighter than the PU foam counterpart, but where the real benefits kick in is the lively aggressive snap off the wake from the machined PVC core. when you shake this type of core, it shakes back. also the strata mounting system is bonded with resin twice top and bottom, so its break-strength has increased to almost double than the 1200 psi that PU core hyperlite decks normally have. The nova core's break-strength is close to 2000 psi. so it is definitely stronger than most boards. plus you can get a wider stance than the normal inserts offer.
I have not ridden the new Murray, but rode the Marek for half the season last year and here's my overall impression. this thing is lightning fast, rolls onto edge almost too easily with little effort required. and its pretty sensitive to respond. once on edge it sits deep in the water, but nice and skatey when flat. pops smooth off the wake, and most people actually feel such sheer speed coming into the wake that it pops them bigger than expected or quicker than what they were ready for. landings are broken up by a molded in landing shape and no speed is lost even in the flats, but doesnt have the "heel-toe" rock when on the swim deck.
I dont think you could go wrong with either of the Marek or Murray though. they are unique but sick rides.