I guess I was asking what skill takes the shortest/longest time to supermax?
For me, it mostly depends on how much your Sim is dedicated to its goal. The more you focus on a skill, the faster it is to reach level 10 and unlock the challenges. If the Sim spends a bit of time on a bit of everything, not only does it take altogether more time to reach the same point, but the wish management will be more complicated and less efficient.
Besides this, EP skills challenges are often a bit more time consuming than the base game ones. The only exception is guitar, and the other instruments with LN. Since one of the 3 challenges relies only on opportunities, you're pretty much dependent on the goodwill of the randomness of the game.
Then, the traits of the Sim can help too. At least to reach level 10 faster, but that's obvious
. But sometimes, traits can also help for the challenges. Angler tends to catch more fish than other Sims, Green Thumb gives a boost to the quality of the plants, Virtuoso receives bigger tips...