Yeah, BIG difference between just finish cat-4 and winning. Here's a perspective from two different cat-4 racers. I lived with a teammate and we did mostly the same training rides, he was stronger than me on the flats, was faster on hillclimbs, absolutely demolished me on time-trials.
We started cat-4 at about the same time. I won my 1st two races surprisingly easily, my teammate was nowhere to be found at finishing sprint. My 3rd race, we figured i'm help him more by following him around and giving him lead-out to finish. Last lap, i come around to lead-out. Second-to-last corner i pick it up to get around first 2 guys so we can be first out of last corner. Look back and he's gone from behind my wheel to middle of the pack! I slow to help him get back on. We get out of last corner around 10th-15th and I realize it's too late, I gottta go. Still ended up with 2nd behind Joe White.
So moral of the story? It takes more than just watts to be 'competitive' in cat-4. My roommate who was clearly stronger than me never scored any points and did 2 more years of cat-4 and quit. I was racing 12P races by then and he was STILL kicking my ass on training rides.