Wishes cruises are OUTSIDE the MK so the castle (which is really "part of the show") is (at least partially) obstructed. Its also much farther away so you can't really discern the "projections" on the castle (like when they turn the whole castle facade into Mickey's "Sorcerer's Apprentice" HAT).
Likewise, Tinkerbell's flight during the early part of the show is likely not visible from most boats.
The SOUND is very important to Wishes and some lower-priced cruises don't "supply" it. (Many times the boats that DO offer the sound will "share" it with other cruise-boats nearby).
But even WITH the sound "piped-in" it does not have the same IMPACT of how the show "SOUNDS" in the park. The power of the major sound-systems inside MK, offers a "surround" effect that is not "felt" from outside the park.
In contrast, the IllumiNations cruise boats are actually INSIDE Epcot and have the benefit of hearing the soundtrack directly from the Epcot audio systems... and THAT is a major PLUS.
There is ONE element of "Wishes" that CAN appear "better" when seen from outside the MK. The farther distance away you are from the fireworks, (say, between a half-mile up to 10 miles away) the LARGER they appear to be!
Wishes fireworks viewed from the beach (or Ohana) at the Poly, appear to be much, MUCH larger than they do when seen from near the hub in MK.
I have a side-by-side comparison on video tape... its almost UNBELIEVABLE the difference of apparent SIZE between the identical blasts.
FWIW:
On a SIDE NOTE about your Poll.
You added "to much information" (IMHO) to the simple "A or B" question.
I would have voted, but adding the "restaurants" part of the question (which I have NOT DONE) caused me not to be able to answer truthfully.
(The reason so many "real" polls results can be "skewed" is that the question was worded in a way that those responding may not have had a "clear and simple" choice to make.)
No biggie.