Probably. I think there's good adaptation from both workouts and good reason to do both. I prefer the latter b/c it's more fun to me and I'm better at it.

I only do a handful of road races per year; my primary focus is crit and track racing I make sure to ride for 5+ hrs every few weeks or so at least. There really is no substitute - it just makes your "bag of efforts" so much deeper. You need to go "ball out" to make things sharp and effective, but without those endurance rides you won't be able to go into the red like that nearly as many times.