Stumpalump,
I've got the first generation Jetboil and a MSR Pocket Rocket, among some other stoves. The Jetboil may look big, but it's all self-contained. The cook pot/cup is only slightly taller than my Snow Peak 700 cup. Jetboil is great on fuel, comparitively, if all you are doing is boiling water. In fact, that's primarily what I use my JB for. I've found if I cook anything other than ramen in it, food will stick to the inside, and the cup is so deep it's tough to clean stuck on food out. I can also crack the top on a can of Chunky Soup and put it in the JB cup with a little less water and heat the soup in 10 minutes and eat right out of the can.
Either stove will simmer, but I use my Pocket Rocket for actual cooking and pan-frying. It offers more options as far as pots, pans, or even the Outback Oven. A lot depends on where you are going, for how long, and how much you are willing to carry. A Pepsi can stove or an Esbit may be your best choice for the backpack and Mountain House. International or long-distance travel may require that you get a multifuel stove; you can use fuel from your bike's tank, as well. Be careful, for as I have found, stoves can be part of the gear obsession we all have here at Expo.
Feel free to ask specific questions and I'll help however I can.