Harry - thanks for reposting that video. The guy who told me about making silicone over foam tires raced 1/32 replicas of sprint cars in PA. Huge rear tires added to the realism.

I learned about urethane and PG tires on HRW, and ALL my Trans Am, Can-Am, and World Sportscar Championship (Le Mans) series cars that race on my road course have PGT's on them. That's nearly 100 cars worth of tires, but well worth the investment. Some of my newer cars have XPG's on them just because I found them to be more flexible and easier to mount.
But in the years before I found HRW when my slot car knowledge was still from the '80's I bought random things from Professor Motor and just because I liked how beefy they were got some silicone coated foam tires. They turned out to work very well on the oval I'd just built so the arms race was on, all the ensuing cars were built using these tires and cars built from RTR parts got MaxxTrac tires. I'm guessing it was the years of 'rubbering' in that track with silicone that explains why they outperform urethanes.
So if I may rephrase what Harry said, "Individual results will vary". I think track location, surface, and history are all apt to play a role in how cars and tires perform. Experimentation is likely the best way to find what will produce the best results.