Depends on what I'm doing, they both have their very good purposes. If I'm doing theory based stuff, Metric can't be beat, since it's our regular base 10 system. If I'm on the floor building stuff, give me Imperial. Shop math is so stupidly easy once you learn it, you'll never want to mess with Metric when building anything ever again. But, our schools don't teach shop math very well, and barely teach fractions anymore, so people don't know the glory that is Imperial. I had to learn shop math in a CAD class. It took all of 5 minutes. The teacher pointed at a line, and asked where the middle would be. Everyone went to get out their calculators, and the teacher yelled "ALREADY TOO SLOW", then moved on to the center of a circle. Everyone turned on their calculators, and again, the teacher screamed "TOO SLOW". Here's the trick with Imperial. You want the center of a line/circle? Say a line 1/2 inches long. Divide by two. Center is at 1/4. Center of that? Divide by two again, 1/8. Center of that? 1/16. On and on and on. Metric? Where the center of a .500mm line? .250. Center of that? .125. Center of that? Uhhh.... So theory? Metric. Practice? Imperial. My teachers up until that class had done nothing but bash Imperial, so once we got to the CAD class, nobody even considered it an option. It was an archaic out of date system that had no use anymore. That quick little lesson made me love the Imperial, and made the entire class realize we were brainwashed by idiots.