Dont know about megasob but we have Aqua-Max and alternate (one week AM one week Flax and so on) it with Flax - makes a fab easy to muck out semi deep litter bed!
Don't know about Megasorb but we've been on Aquamax for 2 years and love it and we get a discount online from horsezz, so we save lots on our costs TTFN Tina
Megazorb is 1000 times better than Aquamax. When we were looking for bedding a few years ago, we ran a test with a small bucket of several types of bedding including aquamax and megazorb, shavings etc. and Megazorb came out of top by miles. wouldnt use anything else now!