I have a 1994 1200 Sportster and I recently test rode a 2008 1200 Sportster, here's what I can tell you. First things first, some Harley dealers let you rent bikes for the day. At the very least you should test ride any bike before you spend thousands on it. You can also find loads of information here http://xlforum.net/index.html
you should also do a search on the web for Harley bike rentals or demo rides.
I bought my VN750 after getting a pretty sick of my 1994 Sportster (even though I have not ridden it since 2001, I still can't bring myself to sell it yet either). The older Sportster (pre-2004) has a deliberately unbalanced, rigid mounted engine. That basically means that not only does the engine shake like a paint mixer, but since it's bolted directly to the frame of the bike, the whole bike shakes like a paint mixer! That's pretty pounding on the rider. I rode my Sporty about 200 miles in one day and popped three turn signal bulbs, a taillight bulb and my license plate tore off where it was bolted on - all from vibration. There are some remedies for this that help somewhat. The belt drive pulleys that drive the rear wheel on those 883 Sportsters had 27 teeth on the transmission side pulley and I think 65 teeth on the wheel pulley. The 1200 Sportsters had a 29 tooth front pulley that dropped the RPMs down by 500 at any given speed to reduce vibration. There are also other pulleys you can find if you look hard enough, like a 55 tooth rear pulley. That will lower your engine RPM a lot and increase your gas mileage to about 60 MPG from what I've read, but your acceleration will suffer a lot too. So right there, there's something you can do with a Sportster that you can't do with a shaft drive VN750 - change final drive ratios easily.
In 2004 HD finally "rubber mounted" the still unbalanced engine so that much of the vibration disappears when the bike is cruising at highway speeds. That was a welcome change, however HD in its infinite wisdom decided that they needed to beef up the Sportster's frame in order to handle the extra shaking of the rubber mounted engine and added 50 lbs more to the frame to handle the shaking motor! So even though the new FI engine may have more power than the slightly older ones do, that power is needed to move that extra weight. The older Sportsters might actually be a bit quicker because they weight less.
So after test riding the 2008 my thoughts were basically: The FI is a nice to have. The Sportster still feels like a piece of farm equipment on two wheels, it's not a precision machine at all. To pass EPA emissions and noise regulations the new Sportsters have very tall gearing so that it felt like it was just barely running above idle RPM in 5th gear at 65 MPH, so the vibrations were low, the exhaust sound was low and the engine lugged! (I recently heard that newer Ducatis are doing this same thing now to get past the EPA regulations too.) The thought of buying a new Sportster in the future crossed my mind, but I'm so happy with the VN750 that it's just not going to happen.
Some pros and cons to consider:
- Large choice of aftermarket parts for the XL (still not as large a selection as the big twins though), so you can customize your Sportster in a million different ways
- You can customize your XL in a million different ways, be prepared to spend lots of money doing that, the temptation will always be there.
- FI is nice to have, belt drive is clean and easy to maintain
- XL1200 felt under powered for me at highway speeds
- You're buying into the HD image, so when people look at your bike and then ask if it's a Harley, you can actually say yes now.
- "You have a shortster? Oh that's a girl's bike, why'd you get that?" - I've heard all of that before
- If you do your own wrenching you'll need to pick up some American Standard tools, they don't have may metric parts on HDs.
- The VN750 will probably beat the XL1200 in the 1/4 mile by a lot
- The XL1200 will probably pick up more chicks (my Sportster got me my wife!)
- Both bikes have self adjusting valves
- VN750 is liquid cooled, the XL1200 is air cooled so stop-and-go traffic really cooks the oil and the rider
- The VN750 shifts like a Japanese bike, the XL1200 shifts like a piece of farm equipment (IMO)
- Stock XL1200 seats are hard as rocks
- XL brakes lack feel, the rear brake is very easy to lock up (IMO)
- 1994 XL needed a good amount of time to warm up before being ridden, if it the engine was not warmed up properly before being ridden the cylinder gaskets would leak
- 1994 XL shook like a paint mixer, the 2008 XL less so, the VN750 has almost no vibration by comparison (IMO)
- 1994 XL clutch felt like it came off of a truck, the 2008 less so, the VN750 feels feather light by comparison (IMO)
- 1994 XL was very reliable... until you started modding it. In stock form it was great, but who leaves a bike stock?
- 1994 XL handling was stable, felt even more stable after adding a fork brace (IMO)
- Working on a 1994 XL was fairly straight forward, although 5 lb hammers are sometimes considered Harley "fine tuning" tools.
- R/R is right out in front on the XL
- VN750 has tubeless tires, some XLs do not
- XL is heavier than the VN750, try not to get into situations where you have to push it far
- Don't believe the hype on the resale value of XLs, they don't hold their value like Big Twins do.
I highly suggest that you demo ride one first before you take the plunge and buy one. While you're at it, also ride the cheapest Big Twin you can find. HD puts a lot more thought and engineering into the Big Twins than the Sportsters and the aftermarket supports the Big Twins a lot better too.