1. Sous-vide offers precise (and easy) temperature control
One of the biggest concerns while infusing canna-oil is the temperature -- if it's too cool, the THC will bind to the oil at a diminished rate (or not bind at all), and if it's too hot, you're vaporizing some of the psychoactive ingredients and losing potency.
"As a general rule, a higher temperature leads to a faster reaction rate and therefore requires less cooking time to be activated; it should be noted, however, that temperatures above 140 [degrees] C run the risk of beginning to vaporize compounds out of the mixture and temperatures below 90 [degrees] C may not lead to significant chemical conversion on a time scale of less than 24 hours.” -- ScienceDirect and Perrotin-Brunel, H, Buijs, W, Spronsen, JV, Roosmalen, MJEV, Peters, CJ, Verpoorte, R, Wikamp, GJ. via Wikipedia
Unlike a saucepan, slow cooker, or double boiler, with a sous-vide you simply input a temperature on the digital display (or your smartphone!) and rest assured, your oil with remain within +/- 1°F of the chosen temperature for the entire cooking duration. No fuss, no muss, and I guarantee you'll get it right the very first time.
Plus, once you've found a recipe that works for you (Sousweed has a lot of great ones) and your material, you'll be able to reproduce it every time. This is great because you'll never have to worry about accidentally wasting your top-shelf bud or hash in a temperature-related cooking accident.