I've found that HW RG3 virtually never misses on a pass, but CV Denard does.
That said, Denard is significantly faster and harder to bring down than RG3, so it really depends on your style of play. Denard may sail 1 out of every 50 passes, so it's a question of whether you want to live with that when it happens for his increased running ability.
Also, I have to say....it pisses me the hell off that there is a better player than a "Heisman Winner." I don't have the Cover RG3, but I would imagine he's better than HW RG3 --- and that makes me angry. If you're going to have different tiers of players, HW should be the highest level for that individual player.