I have been going through this same delema. You really have to weigh out the pros and cons and decide what is right for you. There are so many decisions to make. Here's some of what I have found out during my investigating.
Stage II supercharger:
Get this one rather than the stage I. Saves you from upgrading later. To acheive decent hp on pump fuel, you will have to get the 9:1 compression pistons installed. ( $700 new ). Might not hurt to get a headspacer as well. ( Not sure on the cost, yet ) Figure on 9hp per 1 lb. of boost. The above set up will allow you 10lb of boost on pump fuel safely. This will equal to about 240hp. You can later turn the boost up to 14lbs, but It is said to use a 50/50 mix for that. ( apprx. 276hp )
You can keep your stock size fuel tank, use the stock exhaust and keep noise levels to minimum. Easier instal and takes half the time. NO MODIFING ANYTHING, except drilling one hole.
Most Turbos:
MORE HP!! I was looking at the powderlites one. But in general, figure on 10hp per 1 lb. of boost. With doing the same thing as above with the pistons and headspacer, you can safely achieve 265hp on pump fuel. This is at 12lbs of boost. You will have less fuel cap. as these front mount turbos include a smaller fuel tank. The only turbo company I have found that has a connecting pipe to use the stock duel exhaust is from Northeast Turbos. The other ones have the exhaust dump infront of the track with the exception of the rear mounts. These are louder than stock, by the way. The powderlites turbo, you will have to relocate your guage cluster to your handle bars as the intake filter has to come up through your dashboard. looks kinda kool, though.
Which ever one you get, you'll also have to invest more cash in preventitive equipment such as gauges. I'm getting the air/fuel ( $400 )
Boost ( min. $60 ), fuel press ( $60), and water temp ( $100+).
These things are very expensive to get. The money for the air induction system is only the beginning. I reccomend you do as I have been for the last month. RESEARCH, RESEARCH, and yes......MORE research. Read through the boosted section of this site as far back as you can and just read all the comments. There are alot of things to consider. Espesially if your going to go through all this just to beat one sled.
Personally, I would do this just to beat my buddy. lol
Which ever you decide, goodluck and be carefull.
They are all good it would seem. It would just simply depend on your style of riding, where you ride and the like.
Please anyone jump in and correct me if I stated something wrong.....
Vince
Cool, I thought I had "most" of it right. This research on this stuff is so intense. My head really hurts. 
