Ronnie, we're booked on this sailing and, from our own personal experience, I have to say we like Princess just a bit better. Princess is a bit more conservative and the ships are understated, however, don't mistake this for being stuffy! Far from it, some of the best laughs I've had while cruising have been aboard Princess ships.
I like the food better on Princess, just be warned in advance that the buffet area can get a little crazy, there is no real traffic flow pattern and it results in some confusion. If you are a pasta lover like me then you'll love the fact that there is at least one pasta dish on the dinner menu every night. And, don't forget Princess offers a 24 hour buffet!
Grand Princess is an amazing ship but, beware of the design flaw. If you book a balcony cabin, be very careful of what you select if you like privacy - as the way the ship is designed, the balcony above you can see clearly right down to the balconies below. What makes this worse is that the mini-suites - an entire deck of them - are exposed to almost everyone above them.
If you can live with this fact then you'll love Grand Princess! I hope you decide to book and if I can answer any specific questions just let me know!!