We have the odyssey. Love it. 2007. We looked at Siennas too. I just have a slight preference for honda's. You really can't go wrong with either one. Test them both. See which one feels better.
We have a VW Routan (it's a T&C) and I love it. So much cheaper and it has low miles and all the bells and whistles - leather, DVD players, navigation etc.
We test drove both when we bought our van and ended up with the Toyota Sienna. I liked how it handled better and it was less expensive for the same features.
We bought a Sienna in December. So far I am really liking it. We went with the Sienna over the Odyssey because I wanted AWD. Otherwise, I probably would have gone with the Odyssey. Not sure how many kids you are planning long term, but the Odyssey has more latch and top anchor/tether positions than the Sienna.
The Sienna only has one tether in the third row. I find that very odd when its a minivan after all! These days with how long kids are in car seats and the demographic of minivan owners it would make sense people would need more than one in each row of seats.
We are done with 3 though so only having one in the third row, plus the two in the middle is fine for us.
As a side note, the AWD model only comes with the 7 passenger seat configuration.
We bought a Toyota Sienna two years ago. We had 1.5 kids at the time, and a large dog. We take long trips to visit family and love camping. It was the best fit for the family. We looked at pretty much every minivan out there (and several three row SUVs too). For us it came down to the Sienna or the Odyssey. The Quest had a lost less cargo space, and the salesman was terrible. The Town and Country was cool with the stow and go, but DH thought it looked/felt "cheap." To get the options we wanted on the Sienna and the Odyssey, the Odyssey was an additional $5k. We did like the Odyssey better, but not enough to justify the additional cost. Consumer Reports consistently ranks the Odyssey and the Sienna as the top two minivans. And now that I typed that I looked it up and I am wrong. For 2014, CR ranks the Odyssey #1, and the Quest #2. Sienna is 3.