In order to profit at HU you have to maintain a high win rate. You'll only ever double you money where as with a 9 man SnG you'll have a chance to win 3 buy ins rather than 1. The rake on these games is rather high as well. That eats away at profit as well so technically you aren't actually doubling your money.

If you can crush these stakes then I would go for it. On the surface it does seem easier since you only have to beat one person, but i'm sure you know that there is a lot of bluffing and speculative play at HU. You will need to be levels ahead of your competition.