The elevator works fine, i got it for 32usd from buy and works just fine for me. The mrain looks nice, i didnt know about it when I got mine. However it seems that the griffin one offers more space beneath it.
About the Mrain being a heatsink, im not sure about it since it looks like the computer is held by some pads between the aluminum and the computer, so heat wont transfer through there.
Definetly the mrain looks better, but I think the griffin one serves the purose, it is strong and it is not meant to push against it (by typing over it) and it does hold the computer as long as you keep the pads clean. Besides, I think the griffin one helps you gain space in your desk, while the mrain seems just to take it. That is my opinion.