af895,
Obviously the shorter you can make the swingarm the stronger it can be and get better energy transmission. So on my race bike the rear tire barely clears the seat post tube and they minized that distance as much as possible but still the tire and rim is much larger diameter so it will never be as close as a 20" wheel.
I don't hate derailleurs and see where they are useful and I do like them for many things. However after my last trip through Germany and Denmark on my Dahon I was cussing the thing as I set there picking weeds out. I could also see bits of sand that had been thrown up on it while riding along some of the coastal areas. Sand will quickly destroy gears, chains, sprockets and dearailleurs. When I got home I must have cleaned at least a teaspoon of sand out of it. That might not seem like much but for a small area it was a huge amount.
I think on the biggest cog on my Dahon, the lowest wheel sets maybe 2" or less from the ground. I just went and measured it and it is 5.1 cm (~2.1 inches) from the ground and that is with a big fat set of Schwalbe Big Apples on it which have taller sidewalls than the original Ritchie Rov'rs. It is pretty obvious why it is an issue for me when it is that low. I was thinking it was closer to 3" but after measuring it I was shocked. I have had to straighten it a few time from being knocked about but nothing major...yet!
I agree that derailleurs are easily serviced but then of course they require more service so they better. I have yet to wear out an internal hub so maybe I'm just lucky or I don't ride enough. On a typical day though I ride about 10-15 miles and most of the mile are on my folders. Weekends I'll put the miles on my race bike but even then that might be 30-40 each day and it is Campy equipped.
I personally would love to see a Rohloff at a lower price point someday. I have been agonizing over springing for one or not. Really the last thing stopping me is that I'd hate to have the bike stolen with it and it would be a prime target for thieves. I can't always take the bike any with me and I always keep 2 locks on it when I am in Berlin. Even then people have tried to cut the pole (rather than the locks) that my bike was attached to. Damn near succeded one time. If they say it had a Rohloff I am sure the effort devoted to trying to steal it would go up.
I want something I can use like an appliance sometimes without a lot of maintenance. Sort of like driving a Honda, put gas in it and change the oil and it goes. Everytime I pack my bike in the suitcase I have to take off the derailleur so it will fit. Then I spend quite a few minuted fiddling with it at my destination to make it work properly again. Even though I have tried to scribe marks where everything needs to go it is just off enough to annoy me. My hub gears never seem to have this issue or not to the extent as my derailleurs. I also like the fact that gear changes are usually more positive on the hub gears than most of the lower end derailleur crap that gets put on folding bikes. I also like the fact that I can shift up or down a gear while stopped.
To each their own but for a while I'll keep both but for commuting the internal hub wins hands down for me.