I'm no pro, but play from time to time for a little extra money. I don't know what anybody's answer here will be, but these are, I think, worth a read http://www.cardschat.com/going…..er-pro.php and http://www.pokertips.org/strat…..ng-pro.php
I think the simple answer to what game is "the game you can make the most money at", but you need to balance that with your comfort level with your bankroll. The games you can make the most money at won't be the ones with the biggest betting structure. You need to figure out what your advantage at the game it. I know people that make about 100K a year playing 1/2 and 2/5 NL. As you said, there are big swings, and they put in a TON of hours, but financially they do ok.
As for the swings, how do you define big? Watching high stakes cash games on TV I've seen people go through many hundreds of thousands of dollars in a single session. if I believe what I've read, some pros have built bankrolls up to $20 million and then been down to owing people money. I think dealing with the swings is part of the job. I think a rational person would say "wow, maybe I'll put 5 or 10 million away and I can lieve off the interest and never worry about money again", but I don't think a rational person would put themselves in a position where they could build a $20 million bankroll in the first place.
I'm really interested to see what other's answers are here.