I can confirm that the black Eneloop XX batteries will have a shorter lifespan than regular Eneloops.
We've done extensive rechargeable battery tests, and have found that the regular eneloops offer some of the best value/$$$. The XX's are great too, just know that you'll get far less cycles out of them before they refuse to recharge.
I still love my FP24 / MixPre for it's size, quality, powering, and features!