Any litre bike il4, even the new r1 is more reliable which is the biggest advantage, delievers power way smoother, doesn't jerk under 4k. Revs (which are often high in racing) don't kill an il4 which is the number one way to destroy a 848/1098/1198 motor. Oh and to make the same power/slightly more stock its way cheaper which is also a design characteristic of a well designed, well, anything. If something is better and cheaper, its usually the one to go with.
Just reiterating, from my history with il4s, I chose to go with the ducati dispite being grossly over priced and under reliable because I don't need absoute performance and I'd rather sacrafice some of the other things for the awsome street motor it has that absoutely rips stumps out of the ground, the unbelieveable sex appeal the bike has over the japs and just how unique the design is.
Edit: your idea about pure production numbers bringing cost down is deffinately true. I just don't know how much of a role that plays with ducati's case being that the RC51 was much cheaper than the ducati which was similar performance back in the SP1/SP2 era of jdm twins