We have a 2.5 and 1 year old boy, and a CPO 2010 Odyssey EXL. The electric sliding doors and lift gate helps so much when my hands are full and my key is just dangling on my belt ring. Hold the buttons and they open up. I also love the auto-roll down of the windows on a hot day when I hold "unlock" after disabling the alarm. My wife can sit comfortably between them in the 2nd row if the kids want her closer while en route. I simply fold down the front center console and my wife can scoot over from the front seat.
Sometimes we haul along the extended family, or guests, and easily fit them inside the van with room to spare. If going on a road trip with all 8 spaces occupied, consider using a roof mounted cargo box. It comfortably seats 8 with tons of 3rd row leg room. Only downside is the ground clearance is only maybe 4" (some vans have it higher). We considered a late model (2008) Pilot, EX-L. It felt too old, and the 3rd row didn't have adequate room (basically useless).
I've driven the 2014 Sienna also as a rental, that thing is too wallowy on the bends for me. Odyssey has far better handling, IMO.
Mercedes Metris is too pricey (starting at $40k when a new Odyssey is $30k). I did look around when I first saw news of it.
If 4-wheel traction is required, Toyota offers an AWD version of the Sienna. The Kia Sedona is a close 3rd option for the new vans, I heard they are pretty good also but not as expensive. IMO the Sedona looks better than the Sienna of the same generation. I can never reconcile the Sienna's design, some angles are good while some are "meh".
When we were looking around we considered the Nissan Quest, and it's by far the worst performer (safety-wise) of the new minivans. We didn't even bother looking at the sister minivans Chrysler T&C and the Dodge Caravan. Seats are too thin and aren't comfortable on long drives, and safety isn't as good as the others.
They are not without their faults, our model is known for transmission problems, p/s problems, etc. Toyota's Sienna (of the same generation) has their own issues as well. I say do your research and pick your poison.
This is just my opinion.