I don't compete with these speedloaders but have both in 44 magnum and practice with them. The SL Variant is by far superior and easier to use than the Speed Beez speedloader. The SL Variant speedloader holds the rounds under tension and releases them with very little effort needed, while the Speed Beez holds the rounds using a spring band that you need to overcome with a fair amount of force when loading the rounds into the revolver.
Also for some reason the 44 Mag SL Variants, at least in the first batch, aren't completely assembled correctly and need to be taken apart; fully screwed together with loctite applied. Here's a picture of a fixed SL Variant on the left and the way they arrive on the right, notice the length of the brass rod that is sticking too far out.