If you're considering the HDs take a close look at the Ameriglos. Have the Ameriglo I-dot Pros on a G17. Great sights and much better priced alternative to the HDs. Mine are orange ringed front which are very easy to pick up. Paid around $90 for the set on ebay. Not a competitive idpa shooter, but run similar drills and they are excellent for that.
Recently shot a friends Big Dots and was impressed. Once I got used to the sights, the big dots were as accurate as stock sights for quick shooting out to around 10-12 yards, but were much easier to pick up. If you were going to try to bare down on something for accuracy or go longer range, then the I-dots are a better choice. Ordered a set of big dots for my Bodyguard 380 and may add a set to my Shield - both carry guns where speed is critical. On the fence between Big Dots and I-dots for the Shield.