Clearly YW and Sea Hag games are going to play out differently, but my argument is that they are of similar power level (assuming the bane is not worth getting). With Hag, everything moves slow for both player. With Young Witch it moves faster. But while you're building up faster against Young Witch, the Young Witch player is building up too, while giving curses.
As an example, I take the "Peddling at the Market" bot in Geronimoo's sim, replacing the Masquerade with a Steward, so it doesn't hard-counter curses. If you put this modified engine bot against Sea Hag or Young Witch, it wins. But if you open Young Witch/Silver instead of Steward/Quarry, and then go into the same engine, it beats the pure engine. You can't do the same with Sea Hag. So one could argue that in this board (Market, Peddler, Quarry, Smithy, Worker's Village, Steward, $4 curser), you can skip Hag but you can't skip Young Witch.
Obviously there are also examples in the other direction (where you can skip Young Witch but not Sea Hag), but I think on the whole it's probably pretty close. I think there's just a greater psychological fear of Sea Hag that keeps people from trying to skip it.