I always preferred foam indoors because it made traction less of an issue, it always felt like we had closer and more exciting racing in the foam classes than the rubber ones. Plus, although I know it's not really true at the pro level, we had club racers who would put on a new set of rubber tires and instantly gain .1-.2 sec a lap. On foam that didn't seem to be the case, we could run old foams and be just as fast, assuming we rotated the tires properly and adjusted rollout properly.
That might have just been the situation at our club, we ran both rubber and foam indoors and after a couple of seasons I definitely preferred foam. It is messy, though, and you need to have access to a good truer. Chunking was also a factor but it always seemed directly related to skill level, as we got better we saw fewer chunks.
For beginner-to-intermediate drivers, I'd definitely recommend a rubber class, no question. Changing tires often won't help while you're learning, so you can do a whole season on one or two sets of rubber. I wish someone had told me that when I started, I'd always buy a new set of tires every couple weeks, and my fast laps would get better but I'd still blow it all in a couple of crashes every week. It never mattered until I got good enough to run a clean 5 minutes.
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