When we were shopping for our current 42C, we toured one private seller's boat with Cummins B (inline 6-cyl, 5.9L, 370-hp) diesels... and he said he found them to be quite satisfactory. Speed figures he put forward seemed reasonable, if true. OTOH, I felt they wouldn't be optimal, so we purposely chose to shop for models with the Cummins C (inline 6-cyl, 8.3L, 450-hp) or the comparable Cat or Volvo diesels. I think our choice was reasonable, given that our boat isn't an actual speed demon even with the 450Cs.
That said, that 38 looks to be something like 7K pounds lighter, so less horsepower could be just fine.
FWIW, the B engines are dry-sleeved (Cs are wet-sleeved) so any future cylinder reboring and so forth (as from some kind of unusual wear problem) would likely have to be done with the engines out of the boat. It's likely easy enough to haul the engines out of that boat through hatches in the saloon and then out through the cockpit doors... so that's likely not a big deal. (I thought it might be, when we were shopping, but have since learned more about how engines come out of 42Cs., engine room hatches, etc.)
-Chris