I just sold the 27" MST's I had. For weight a 27x12x12 weights 32#. I don't know how they compare to other tire weight. I really like the MST tire. The only reason why I got rid of them was that I had to many tires laying around and it was in between sizes. I'm running 26" Bighorns on the trail and have a set 0f 28" Laws for the mud. I couldn't justify keeping the MST's.
If a person was going to limit themselves to one set of tires I would highly recommend the MST's. To be honest I wish I bought a smaller set instead of the Bighorns I'm running now. The MST's were smooth running, stayed clean and did a nice job clawing through the mud.
I had them on my 07 brute and loved them.They rode really well and pulled good if you got in some bad stuff.Air pressure is the key to that tire though,I found that around 5psi was about perfect for it