There's not much real difference in most of them if you look at the ingredients. The main difference IMO is those that use Na-R-ALA and those that don't. Glycobol and Need2Slin do, the others do not.
Norvaline is used in SlinSane and Need2Slin to increase vasodilation and increase pump. You can use any of them to increase pumps pre-workout, just dose it with carbs 30 minutes pre-workout (NP 60 minutes pre-workout) and you get good food pumps.
Recompadrol kinda falls into a 3rd category since it uses HCA (prevents adipogenesis) as well as the usual gymnemic acid and corosolic acid found in the rest of the products. Berberine is another component in Recompadrol and Glycobol, but my body/GI does not agree with berberine...
Need2Slin is also unique because of the cAMP pathway it uses for partitioning as well as fat burning (forskolin). It gave me the best results, especially when stacked with NTBM Gear which increases the bioavailability of protein, which was then shuttled to the muscles by the N2Slin. Great combo IMO.
So, they all basically use the same pathway, but Na-R-ALA, gymnema and corosolic acid (banaba leaf or lagerstroemia (which is crepe myrtle)) are the superstar of nutrient partitioning IMO, and good for overall health. (also 4-hydroxyisoleucine found in fenugreek and pterostilbene, but no one seems to include it yet)