I am not familier with SIDI Mega Rain Boots, BUT I have a pair of SIDI ON ROADS. They have over 100,000 miles to wear out the factory soles, I had them resoled with 1 inch additional sole added to them. THey are still pretty much waterproof, I have started applying a high quality leather dressing to them now as a attempt to help them continue to do a satisfactory job. Expensive ? yeah somewhat at initial purchase, but I got what I paid for, well built waterproof, with very good protection. The Boots Aerostich sells are built by SIDI , called Combat ETC . They are quite similar to the ON ROADS, which I think may have been discontinued/
Eldon