Symphony is definetely a great ship, number 3 after Oasis and Wonder in my opinion.
But here are some great features of Odyssey
Music Hall is a great venue for entertainment, the sheer size blows the Oasis versions away.
Playmakers is huge and climate controlled. Lots of huge screens to watch sports
Giovanni's Wine Bar is great for people watching and reasonable snacks
The pub serves snacks as well
Hibachi has great views, mainly before it gets dark. Rare in winter season, but probably great in Alaska
El Loco Fresh is an improvement over the Oasis ships
Well done Windjammer, on par with Wonder
iFly is a must, so much fun. Pay sessions are cheaper than land based ones
Bumper cars are a blast as well
Outdoor seating on Promenade
Cafe270 is a Park Cafe on steroids. Great seating in 270 as well. Watch them rehearse for The Book
Solarium is nicely done, on par with Wonder
Great Scooner bar, less distraction than the Oasis ships
Sorrentos seems bigger than Oasis ships