Some practical considerations:
For practice ammo, ball ammo is hard to beat. If your defensive round is jhp it's very easy to find ball ammo in the same weight, velocity and that shoots to the same point of aim in ball ammo. If the jhp costs $25. for a box of 20 rounds than the ball can be found for $12. for a box of 50. Most shooters shoot their defensive loads occasionally at the range but reply on fmj for practice, drills, etc. This saves a good deal of the cost.
Finding the equivalent in a 90 gr. Lehigh Extreme is a bit harder. A 115 gr. fmj that hits the same velocity and shoots to the same point of aim is, I assume, harder to find. Though I admit I've not tried that. Consider the same for 40 S&W or 45 acp.
So, right now the Lehigh ammo cost about the same as quality jhp ammo. But locating less expensive practice ammo may, in some cases, be an issue.
Right now most quality fmj ammo is very good. It's built to perform to the standards for penetration and expansion, after passing through specific barriers, set by the FBI back in the early 90's. It has set a high standard. Penetration is also set to be limited 12 to 18" after passing though barriers. Since the Lehigh ammo is built not to expand it's more difficult to judge it one against the other.
The screw driver shape of the light for caliber bullet, is there to increase the damage to tissue done by the bullet as it rotates. The bullet must penetrate through whatever barriers there may be, including clothing, and still spin with enough energy left to cause the additional trauma to the tissue. Once encountering an object the rotation of the bullet will, in material and flesh, cause the spin to slow and the round to expend a greater amount of energy than a fmj round in both spinning and penetration. Like the expansion of the hollowpoint the spin will retard penetration as it expends energy. It also does not have as much momentum to assist the penetration as a heavier round would. How much energy and how and if this affects performance is a question I have.
So right now I'm still looking for the up side to this ammo that makes it a practical choice for regular use.
Also I always look funny at anything named Extreme!