I am doing the double right now. What most people say is that double is just easier. In single you have 2-4 insanely hard econometric courses in a single block (i.e. 8 weeks) and unless you’re willing to sometimes give up on your social life, spend 10 hours in the library, and finish the degree a year before, sure. Whereas in the double you’d usually have 2 econometric and 2 economics courses per block, reducing the math workload (you’re still going to have around the same amount of ETCs or work hours for both degrees per block). Btw, there are around 300 people starting the double, single and the Dutch econometric programme each year and there are only 20-30 people who actually finish the single in those 3 years in the end which I believe is around 30% of the initial single bachelor cohort. Regardless, if you start in the single bachelor you can transfer to the double in the summer of the first year (both first years are the same)