I've sold both brands, both great vehicles and neither will disappoint. Both are essentially bulletproof if you maintain them properly.
But if I had to choose one over the other, Honda wins.
I like the way it drives more so than the Toyota, it has a bit of character to it while the Sienna is bland in its personality. I'm not a big fan of Honda's new fighter jet style interiors but it works well in the Odyssey. The Sienna is quite dated in its controls/layout in comparison.
Newer design, better more modern tech, looks better (imo). The functionality of the seats is much more adaptable and easier to use for different requirements as well. And you can get it with a shop vac built into the trunk, not a big deal until the kids spill cheerios everywhere or that potted plant falls over. One of smartest features on a van ever imho.
Toyota does offer all wheel drive, but it's an expensive and rare option.
The deal breaker for me is that Toyota STILL doesn't have android auto, although they do have Apple carplay. Honda has both.