I found Cat. 5 racing to be incredibly more aggressive than even my fastest club rides. Lots of jockeying for position, because good positioning is a big part of successful racing. No one will let you back in if you lose your spot. No one cares about being smooth or steady or whether their surging is annoying you or making you suffer. It's an every-man-for-himself freeforall.
I found the cornering to be measurably faster than even my fastest club rides because there is more risk-taking, the roads are generally closed to traffic (so you're not worried about sliding out in a turn and getting hit by an SUV), and corners are where you can make or break a race (especially in crits.).
I found the pace to be faster, LONGER than my fastest club rides. In club rides, even fast ones, you invariably hit a stop sign or traffic light, stop and wait for the guy who flats, take a pee break or a water break, or just let up because no one wants to suffer for too long. In a real race, you never stop till the end. You're always going fast, and then even faster, and you never get to fully recover. I've coughed up blood in crits. which I've never had happen in a club ride.
But racing is such a RUSH!
Bob