I've run my car my both ways.

On my car, huge advantage above 100-110 mph. This means it is a big deal at Roebling, VIR, Lowe's etc. CMP is the only place where I don't think it helps. By huge advantage I mean an additional 300-400 rpm at the end of the straight.

I have seen some data somewhere that said a HT was worth 2 seconds on a Miata at VIR.