I've made decent money at both now, but I've moved from almost exclusively playing SnG's (with a rare MTT thrown in) to pretty much exclusively playing ring games (In fact I am usually either 6 or 9 tabling $25 NL ring games now... hoping to move up to $50 nl very soon). When I played SnG's I would typically play 2-3 at a time (mostly $20, 10 max).
They play style is definitely very different for each and I think some people will be far better at one than the other.
I've done well at both also. But here's what I've found. Ring games are more consistent money and higher $$ per hour if you can adapt to them from tournaments. But you have to be able to control tilt. Tilt on one hand and lose a buyin and you are absolutely killing your profit rate. This isn't quite as big a problem at sng's.
So.. basically rings seem to be more consistent money and more money for me. SnG's can be good money but the variance is far higher. Having an extended out of money streak isn't all that uncommon for sng's even for good players. But different people will probably get different results, this is just my observations so far.