OK. I think it is time for a "devil's advocate" statement. Just to be clear, I own an R27, and I bought it after looking carefully at the R27 and the NordicTug 26, so obviously I made the "right" choice. That said, I don't think the situation is as black and white as some of the posts indicate. The N26 is actually a bigger boat than the R27 -- it is wider, deeper, and, I think, heavier. In serious weather it is likely to be a better, more comfortable, and maybe safer ride. True, it is slower, and those who count on out-running bad weather may take comfort in the R27's greater speed. (I'm not among that group.) Frankly, had I the option, I might have ordered either of the boats with a smaller, simpler engine -- I am not a fan of the new electronic diesels, which seem to have reduced diesel reliability to that of gas engines, and the recently uncovered problem with the oil line in the 4BY2 series does not improve that engine's image.
The layout differences are personal choice, although, in my devil's advocate role, I will mention that the visibility aft on the starboard side of the R27 is really lousy. I don't think the NT26 has this exact problem, although I don't know how its aft field of view works out. The NT26's layout puts the engine in the center of the boat beneath the pilot house. This probably allows for a more horizontal shaft angle without introducing the bulge in the bottom of the boat that the R27 has, but it also requires a longer shaft. I don't know the trade-offs. FWIW, I don't think engine access is very good in either boat.
The R27's layout enables and features the "cave." I can't imagine anyone actually expecting to sleep in that space, advertising claims notwithstanding, but it does provide useful space for long skinny things like fishing poles. I think that kind of stowage space is seriously lacking on the NT26.
The NT26's side doors are a convenience not to be overlooked. The trip to the foredeck on a R27 can be an adventure in any kind of waves, although I confess that I haven't yet looked into arranging a ladder out of the forepeak hatch.
The big difference is, of course, price, and here the R27 has a big advantage. Many (almost all?) of the features -- an example being thrusters -- that are standard on the R27 are expensive options on the NT26.