It depends on the drum clutch, and how its tuned. We knew it was going to happen a year before our track was going to drums, and we decided to run a drum in a sea of disc clutches. Everyone sang the "you will suck on starts" song.
We finished 2nd in points that season,
Fact of the matter is discs grip better than drums... look at your cars brakes for a larger example.. but we are talking about locking up 10 horsepower or so.
Run it, you might wind up liking it more than you think.
We ran Hilliard stuff, btw. Reliability was fantastic (unless you drove it in a parade ... but thats part 2 lol)