I bottle condition most of the time because I only have the ability to keep one beer on tap. That being said I have never natually carbonated anything in a keg, even if it is something that needs alot of aging I just wait to tap it then force carb it.
I invested in money to pay for a kegging system, so I keg and force carb.
However, I've been collecting Grolsh bottles (The way I figure it, I'm buying flip-top bottles and paying $0.99 to have them filled with beer) so that I can bottle stuff to age, archive and share. Flip tops and carb tabs are cheaper than a bottle filler considering how often I plan to bottle.
I'm going to soon investigate natural carbing in kegs though since I've just killed a BRAND NEW #5 CO2 tank to leaky kegs I thought were carbing.
I keg and force, or keg and not, or keg and prime. Mainly, it's keg & force carbonate enough to get it to the tap. I've got one (WDB) now that was 1.004 when kegged. No CO2, no priming sugar, but I'll get 90% foam with a 12' line. And it's still 1.004. No infection, either. Go figure.
I guess I'm the oddball here. I always bottle with Kraeusen and carbonate naturally in the keg. The latter is done with Kraeusen before lagering. I like the beer to be carbonated as soon as I push it over to a serving keg. It also makes sampling from the lagering kegs easier since I don't have to hook-up CO2.