In theory a parallel tip will be stiffer in the tip section. That being said, it’s kind of difficult to compare because of length and weight differences. The Nippon product is easy to compare because they are all discrete length and the same weights. In Nippons case, the shafts are basically the same, .355 vs .370. Same lengths, same weights, only the tip size difference. A Dynamic Gold taper tip .355 will be a constant weight at a specific length. Taking a Dynamic Gold parallel .370 tip shaft, trimming it from the tip for flex will make the weights vary from club to club and each will leave a different amount of parallel tip section length on each iron, which is how parallel tip shafts work to accommodate the different head weights at each length. Still, they will be different weights. When we have run profile numbers on 41 inch blanks of a .370″ and a 41″ .355 parallel tip option, there isn’t much difference but the geometry tells us that the larger tip should feel slightly stiffer to a player with a refined sense if feel. Over the years we have blind tested and found that most players (by a high percentage) can’t tell the difference. It is important to understand that in steel, all irons start out as parallel tip. Taper tip shafts are created by reducing the tip size through specific tooling dies. Graphite shafts are basically sanded down to .355 from .370.
I think the fact that taper tip sets are constant weight is more of a reason better players may prefer a taper tip model vs a parallel tip model that is usually (except for many Nippon shafts) not going to be a constant weight once they are trimmed. Profile wise, Jim says and I agree, overall not much difference with the only slight variable being that the larger geometry might make the tip slightly stiffer. Whether the player feels it or sees it in the ball flight is totally dependent on the player. I’ve played both. Can’t say that I can tell the difference.