Well, I am going to be very biased on my answer and say I prefer foams.
On my local 10x15m carpet track, foams work better for all the fastest racers than any rubber tyre, as lots of turn in is needed on such a tight track.
We cannot seem to get a hard compound rubber tyre to heat up enough to get traction, a softer compound tyre will overheat on the sidewalls and grip roll or just not perform consistantly enough to feel confident in.
With a set of hard foams, (40 shore front and rear) the grip is comfortable- Predictable for me as in practice and qualifying round 1 I will use additive, the car will push a little when really nailed.
but then rounds 2, 3 and 4 and the final I wont use any additive as enough has already got onto the track by other racers and the grip has come up nicely, and the lap times go down.
Not every track you will race at will be like this. It works for me, but might not work for you