I have done both the Grand One and the MK fireworks cruise (twice) but have not yet been able to get the Illuminations cruise.
We booked the Grand One for my sister's 20th birthday and had a cake on board (had dinner at Cinderella's Castle). The captain and attendant were wonderful and truly made it a once in a lifetime experience. We had a great time (and great views) on the MK fireworks cruise as well.
I definitely prefer the Grand One.... it's unbelievable but pricey.