I would say there is almost no difference between the two. The Marine-Tex may be slightly easier to file. But not by much. The biggest difference is that if I used JB Weld to begin with I would not have had to do it over. JB Weld is rated to 500 degrees. It even says 600 degrees for short periods of time. It would not have been affected by Chris heating the block to 500 degrees to change the sleeves.