The reality is that there's not a huge difference between an Alpha 6A, and a Monster trap with a Range Limiter and Scatter Plate installed. The monsters have the plate under the cloth, whereas the Alphas have the plate external to the cloth. And, the Monsters have a built-in airgap so appear to be a bit thicker, but the actual absorbent material is equivalent on both.
The Alphas also give you 3 different diffusion patterns to choose from, whereas the Scatter Plates just come in one type.
Apart from these minor differences, performance is quite similar across the board. It's mostly an aesthetic difference -- do you want to see cloth, or the Alpha plates on the front of the panel?