I'll just re-state the obvious: you have nothing to lose by bringing a title (if, like NY, the title is your actual ownership document), much to potentially lose if you don't. Registration does not prove ownership in the USA; it proves current registration, fees, etc. Only the title proves ownership.
Lots of people get by with just a registration, but then again some don't. Some never get asked for their title; others find it's required at every border.
The above does not apply if the bike is registered in a place which doesn't provide titles. In that case, bring whatever document proves, and allows you to transfer, ownership.