I dont know much about poker as I have only been playing it for 3 months, so all I can do is relate my experiences so far.
I started and still love 2.50/6player sit and goes where two get paid- 9+6. I started them a few months back and my ROI is at 32%. This is not spectacular, but I am happy as a beginner. What I found about them is that if you are tight and like to be able to wait for good cards, then don't do turbos- a bad run of cards, one lost race, or one bad beat combined with the rapidly rising blinds could leave you shortstacked and pushing with muck. However, this kind of game suits some people really well. I'm not saying that one shouldn't play them- I guess it depends on the kind of player involved, and I am really only saying what works for me.
I also found that at this low level, there are plenty of fish and maniacs that allow you to get paid off when you get a good hand.
The downside for me was the psychological whack when I finish just outside the money. All that effort for jack sh-t. It is even worse when it happens due to someone getting seriously lucky. Another downside is that I don't feel confident enough to multitable- if I was good enough to do that, my bankroll would increase significantly faster.
Recently, I have been getting into cash, which is also relevant to your original question. Again I want to stress that I say what I say with the obvious caveat that I have only been doing this for a short while and that what works for me may not work for you.
I got into cash because I learned a bit about the kind of poker style that suits me. I want to be able to go into any hand with a reasonable expectation of making a profit and without being pressured by the blinds to make a move. In cash, things are much slower, and that suits me. I can wait for the kind of cards I like to play, and I can make the right mathmatical decisions while knowing that losing a particular hand will not cost me my tournament life.
Basically, I play at very very low limits, as I am still learning. I play 9handed 4 NL- blinds of .02/.04 and I only play one table at a time. In the few weeks that I have been playing it, I have done ok. I have not compiled the records yet, but i have been profitable on 13 of 14 days and usually leave with over 4 dollars in profit after playing about 130 hands. I don't know if this is good or bad because I have yet to find out what the standard expectation for profit is. All I know is that there is way less variance than in sit and go play so far, but based on such a small sample, I don't fell like I can start pontificating about anything.
Having said that, I do think that good tight patient play without being really advanced or clever will yield profits in micro-limit games. I have found even more madness in this game than in the sit and goes. It is not uncommon to see players going all in with the likes of A 10o or KJ, and if you are around to take advantahe, you can do really well. What I would say is don't freak when the numbers betray you and you get a bad beat. I have had my Aces busted by a guy who called with Q8, but I still win enough hands where I am favorite to be profitable. On my worst day, I had that bad beat plus I also had my full house busted by quads, but most of the loss was paid for by profits already accrued, and I only lost about 4 dollars overall. Overall, the style of being patient and only playing premium hands has been paying off, and it is easier for me to play this strategy in 9 handed cash games than in 6 handed S&Gs.
Right now, I can say that I plan to play a lot more cash. I like sit and go games, but cash seems to suit my style. However, I am not giving up sit and go games- I think I'll play them less frequently, but for 5 instead of 2.50. I also want to slowly get into 10 NL, but I still would still like to play for a bit longer at my current level. This is because I have yet to lose kuch there, and I really want to see how I would react to a bigger loss. There are bound to be quite a few and I want to to see if I can have confidence in my current approach to risk management. I have a mental stop loss of 8 dollars per day, but I have no idea if this figure is an appropriate one. It might be too tight or too loose- right now I don't really know, so I can't really say a lot about it.
So with regards to your question, I found that it is best to try both and then see which one better suits your style of play. I found that cash suits me better.