These two products are for two different issues.
Sportlegs attempts to improve performance through the supplementation of lactate. The calcium and magnesium content are secondary and present due to being bound to the lactate as a salt. The thinking being that 1. Lactate can be used as fuel and 2. The presence of lactate tends to decrease blood glucose and glycolysis with the thought that this pushes the body to be more aerobic in it's energy production. Therefore, producing less "Lactic Acid" and therefore "soreness". It's relatively understood that lactic acid does not necessarily cause soreness. Exogenous lactate supplementation has not been widely studied. Oral ingestion tends to show no effect on performance. There was a study that utilized a lactate infusion as an additional source of carbohydate that was beneficial, but with significantly more lactate than in Sportlegs pills. There may be more studies, but I can't remember off the top of my head.
Endurolytes (exteme) are an electrolyte supplement meant to replace lost minerals. In some regard this is more controversial than the above, in others regards, less.
I talk a lot - Give it a listen:
http://www.fasttalklabs.com/category/fast-talk I also give Training Advice via
http://www.ForeverEndurance.com The above poster has eschewed traditional employment and is currently undertaking the ill-conceived task of launching his own hardgoods company. Statements are not made on behalf of nor reflective of anything in any manner... unless they're good, then they count.
http://www.AGNCYINNOVATION.com