Are you buying new? I can compare the 2005/2006 Odyssey to the 2004/2005/2006 Sienna. I was torn between the two as well, as many mini-van buyers today are, and went with the Sienna XLE limited. I love my van!!! I have had it 3 weeks and am so happy I got it. The Odyssey EX-L is comparable to the Sienna XLE with leather and side curtain airbags....but Toyota has so many different packages it is hard to tell somebody in plain english which Toyota it would be. Haha, it is confusing! The Odyssey is more of a sporty van and the Sienna is more of a luxury van...my sister calls mine the lux-o-van! What sold us on the Sienna vs. the Odyssey was the xenon headlights, more top tethers(and LATCH sets I think), wood grain and wood grain steering wheel, and the overall feel of the drive. Also I did not want run-flat tires and on the Odyssey to get the power rear hatch I would have to get the Touring which only has the run-flat PAX tires and on the Sienna I could get a Limited FWD with no run-flats and have the power rear-hatch...a must have feature IMO. Both vans are great vans and it will be a hard decision I am sure. It helped to me read up a lot on both vans at oddyclub.com and siennaclub.org before making my final decison. Good luck and post back if you have any ?? about the Sienna and I would be happy to help!
~Danielle