Ballet is excellent for developping those small little muscles you weren't aware you had, and for developping good posture and balance. It will also stregnthen your torso muscles -- you will never have to do a sit up again if you train regularly and corectly (your pelvis has to be in the right position. Ask a teacher about it if you do take up ballet)
Contemporary really depends on the teacher, so I wouldn't advise it. Besides, usually the point is not so much to get fit so that you can do a set of movements, but rather to see how you deal with difficult movements. I've done both classes where you come out unable to move the next day, and classes where I could go on for hours--no force was being used.
Modern (Graham) will really stregnthen your core muscles in your torso, but not so much in the rest of you. It's great for coordination.
Cunningham's modern dance will give you the same workout as Graham's technique, as well as the main aspects of ballet-- combined. (Ballet still has the advatage of working on the most detailed forgotten muscles, but within 3 months of cunningham's technique, training regularly, you will see a change in your body, and find it eisier to integrate into a ballet class)
Jazz is a little more "arobic" and works less on the minor, core muscles, even though any body who has good basics in ballet has an easier time with some of the jazz movements.
African is really areobic, and will really stregnthen your arms, and back. Make sure you use your back correctly though: if you don't, you will really hurt it.
Hiphop is great for the same things as Jazz and African, but if you do breakdancing, you have got a double plus!!! You will become extremely strong.
Salsa is like walking briskly for however long the class lasts. 2h salsa = 2h walking briskly.
But I hope you realize that the difference between dance and sportsy areobic or weightlifting activities, is that dance's primary consern is how you do the movement, what techniques do you find to make a difficult movement seem easy, and express something. How do you use the minimum of muscles to achieve the same result. How do you relax one part of the body while the other part is working to it's extreme. Then there is ofcourse coordination...
Dancing has made me stronger and fitter. Made me loose an inch of fat. Gave me an iron strong belly without ever doing a sit up, has given me strong cardio-vascular ability. Has given me better balance, and super muscular legs. And more flexible!
But really what I was looking for in dance was greater expressivity with my body and body awareness. I got both as well.
Oh and I used to sweat a lot in beginner ballet, (my clothes soking) now even in more advanced classes I don't sweat nearly as much. And in beginner classes -- I never sweat anymore!
I have watched people do a cunningham style dance class, (3x a week) and with in a year have a "dancer's body".
I also knew a girl (aged 22) who did beginner ballet for the same reasons you are looking to do dance. Over a year I saw what progress whe made! (1x a week. But she didn't make it to the "dancer's body" type)
