I own a '99 K1200LT but I'm the service writer at a Harley-Davidson dealership, so perhaps I can lend my 2 cents. Stuff that breaks on a Harley doesn't seem to be the same stuff that breaks on a K-LT. From what I've seen on this forum, on a BMW you will likely never have to go deeper into the engine than a valve adjustment. But Harleys have automatic hydraulic valve lash adjustment that requires no periodic maintenance at all. If you ever have a head gasket leak on an HD though, you must pull the cylinders off the engine, install new piston rings, and new cylinder base gaskets because the headbolts go all the way through the heads, down the cylinders, and into the crankcase. Loosening them loosens the whole cylinder and necessitates new gaskets or they won't seal once re-torqued. This may need to be done after 30-50k miles. On about the same schedule as final drive replacement on a BMW, in other words. But cheaper.
So I'd say from the maintenance and cost of ownership standpoint, they're a wash. A modern HD touring bike might be marginally more maintenance intensive than a BMW, but the services seem to be less costly to perform. The style and comfort are a personal choice - I suggest doing the old pepsi-challenge and riding both back to back. If you absolutely LOVE the way an HD looks, the K-LT is gonna be lost on you and vice versa. I think both are 100% successful in achieving their stylistic goals.
Ride quality is highly subjective also, of course. Again, I like them both. They're just... different. Chassis changes made to the '09 and up HD touring bikes have yielded huge improvements in stability, rider confidence, and handling. There is room for improvement still; just as Ohlins will improve your BMW, so will Progressive Suspension and RaceTech improve your HD. Either bike will willingly drag it's floorboards/pegs in a very linear and predictable manner in the twisties. Either will feel very good to you when ridden in the manner that the bike itself promotes. For the aggreessive, discerning rider, the K-LT is at once more stable and playful in a way that the casual rider may not appreciate. And for sustained, very-high-speed riding, where the Harley is reaching the edge of it's envelope the BMW is just starting to really smooth out and spread it's wings. HD's may breathe heavy at the top end, but they have a low end grunt that can only be had with big pistons. You'd have to do something really hamfisted and abrupt to stall a modern HD big twin.
Passenger comfort is a no-brainer win for the K-LT, but ergonomic improvements were made on the '09 and '10 HD touring bikes for the benefit of the passenger, so you may find the race to be closer now. That big rubber-mounted v-twin produces a lot of vibration at low speeds and at idle, but it's high amplitude, low frequency vibration that most motorcyclists prefer to the low amplitude, high frequency buzzy stuff that inline 4s create. Once up to speed, the rubber engine mounts actually mitigate vibration very effectively and very little vibration of any kind makes it's way to the rider. Fly-by-wire throttle and Brembo ABS brakes make your job as operator of the HD very easy. Weather protection is an area of profound victory for the BMW, though.
I bought my K-LT solely on the basis of it's price as a used, 10 year old bike. If I was to get a new Harley, it would be a Road Glide. And I absolutely LOVE riding my K1200LT. It's got to be the most rider-oriented touring bike I've ever ridden. But if I had money for a new bike of this class, I wouldn't buy either. I'd get another Goldwing, of which I've had 2. Wing 1 was an '84 1200 four and Wing 2 was an '88 1500 six. I ran each to nearly 100k and other than brakes, tires, and fluids, I never spent DIME ONE on those bikes. No mechanical failures. How is it that Honda can build bulletproof engines AND drivelines, and then combine them in one chassis that can ROUTINELY rack up 200k miles with mechanical failures numbering precisely zero? And how is it that HD and BMW, two companies that have been in the game for a combined total of nearly THREE AND A HALF TIMES the length of Honda's very existence have failed to crack the apparently enigmatic code required for reliability of the most important and basic systems on the bike? I don't know. In the GS forum, I see some guy with a recent R1200 has gone through 4 final drives in 100k miles. That's just perverse. My theory is: these companies do it because we let them get away with it. How many people have wiped out or nearly done so because their final drive dumped gear oil on their rear tire? I'd like to see a Toyota-style uproar directed at BMW. Since they only sell like 4000 bikes a year here or something, I suppose that'll never happen I think if 4% of anything major failed on a Honda, people'd be throwing themselves off Tokyo bridges skyscrapers. Look how fast and thorough they were when the new GL1800 frames had problems.
Buy a Harley if it moves you. Buy a BMW if you want to get moved. Buy a Goldwing if you really like riding motorcycles and just want to keep doing that as often as possible for as long as possible with as little hassle as possible. Oh yeah, and buy a Victory Vision if you want a noisy, hot, squeaky, chintzy thing that feels, looks, and rides as if it were designed by a bunch of very skilled, intelligent people that never talked to each other.