There are more than 2 choices.

The special is essentially a factory mod. It's probably the best "stock" motor out there, especially on big tracks.

I actually prefer a good modded 35+21 to any of the flashes. More bottom with almost as much top.

If you're not an A-main driver or run on tight or parking lot tracks, don't waste your money on either. Get a Kangaroo. Cheaper, nearly as fast and the reigning ROAR Nats champ so it can definitely get the job done.