I have ridden the Erie Canal trail end to end several times and the C&O. As mentioned above the Erie is well developed and currently about one third of it is still on pavement. The only C&O like section of the trail is a few miles between Syracuse and Rome. 28's should be fine dry, but if it rains some sections through the Mohawk Valley are poorly drained and the trail gets spongy , I would choose the 32's
BTW You also have the option of riding an on-road adjacent route "NY bike route 5" which is often more interesting and has 3 foot or wider shoulders for most of the route.
https://www.nysdot.gov/divisions/ope...outes/rt5.html