Hi Pete!
A summary take:
The SON28 Klassik and the SON28 (new) are essentially the same hub with virtually the same output in my testing and in the figures published in the past on the Schmidt website.
One has to be careful not to confuse the SON28 with the identical-appearing SON Deluxe if they wish to use the dynohub to charge gadgets. For powering LED lighting systems only, the SON Deluxe is fine and has lower drag (though drag is essentially unnoticeable on all SON dynohubs if you're touring).
If you wish to power gadgets, get the SON28 Klassik or the SON28 (new). Even so, you will need to turn off any lights when powering or charging gadgets so they will get the hub's full power. For this reason, most people set up their charger leads with piggyback connectors at the hub -- one lead goes to the lights (which are switched) and the other lead goes to the charger.
If you wish the lowest drag and will only be using LED lights, get the SON Deluxe. It is not powerful enough for charging duties. I would urge the first two for greatest versatility if your future needs change.
The SON28 (new) has the "round ball" hub shell and supposedly has a smidge less drag than the Klassik. Output figures on the Schmidt site showed the same output on the (new) as the Klassik the last time I checked. The Klassik has the large, barrel-shaped hub shell that resembles a Rohloff hub. The ball-shaped SON28 (new) has less interior volume and supposedly suffers less from condensation in temperature extremes -- but that really is an academic point, as the Klassik already has a compensating vent in the center of the axle that allows the hub to "breathe" and vent properly (this is why a hub skewer used with a SON hub must never be greased in the center, where it could clog the vent and void the warranty).
So...this is how it shakes out for most uses (small-wheeled recumbents and folders are better served by other SON models):
• If you want minimal drag on a go-fast bike and you'll only use the hub to power LED head- and tailights, get the SON Deluxe.
• If you wish to power gadgets, or light halogen or LED lighting systems and want the most power and will accept a greater but still virtually unnoticeable amount of drag, then get the SON28 Klassik or the SON28 (new). The choice pretty much depends on whether you prefer the ball-shaped hub shell of the SON28 (new) or the barrel-shaped hub shell of the Klassik.
Don't forget, the SON hubs come in a variety of colors. There's a polished silver (aluminum) that requires some maintenance to keep nice over the years, and whose finish can corrode when used on salted roads or near the sea. There's an architectural-quality black-anodized finish that is essentially maintenance-free and will look nice for decades to come. There's also a nice, deep anodized red that matches the red Edelux headlight and red Rohloff hub.
Schmidt Original Nabendynamo (SON) hubs use deep-groove cartridge bearings with shields; quality is roughly comparable to Phil Wood bearings. However, the SON bearings are not field- or user-serviceable. The hub must be returned to a distributor or to SON for bearing replacement.
I have owned the SON28 Klassik and now have the SON28 (new) on my Nomad. I loved both and consider them essential touring gear. The drag is very minimal, even when powering gadgets (roughly the equivalent of climbing about 7 feet over the course of a mile, as I recall).
I am not aware of any difference in strength between the SON28 Klassik and the SON 28 (new). However, the SON28 (new) *is* available in a wide-body version that has a wider hub shell with more space between the flanges to better resist side loads. It is sometimes spec'd for tandem use or by companies like Idworx who wish to maximize strength whenever possible. The wider flanges do give a greater bracing angle to the spokes on each side, but at the cost of some side clearance of you have a Thorn Low-Loader MkV or Tubus Duo lowrider rack and fasten it on with largish hex-head bolts on the inside of the fork legs.
While the q/r SON hubs come with a bolt-on skewer, I have found the skewer tends to loosen in practice in my own use (Schmidt advise a low torque to fasten it) I replaced it with a standard Shimano cam-type q/r (also set with low torque to close) and have had no further problems with loosening.
Some people with sensitive hands on some bikes with some forks at some speeds on some road surfaces have reported an irritating vibration through the handlebars at speed with the SON dynohubs producing electricity -- apparently due to magnetic eddy currents inside the hub shell. This seems to require the "wrong" combination to produce an irritating level of vibration and doesn't bother the vast majority of riders, but I have felt it occasionally on some others' bikes and it can indeed be irritating -- especially on smooth roads. Mine have not produced the same irritating degree of vibration, but I can feel a tiny bit of vibration through the handlebars when the hub is powering my lighting or charging while riding on very smooth roads at some speeds. I mention it only because it has been a "stopper" for those rare few who are severely affected.
Again -- I would suggest getting the SON28 Klassik or SON28 (new) instead of the SON Deluxe, as the more powerful hubs are the most versatile and you may someday wish to power a gadget or charge batteries, and the lower-drag SON Deluxe won't allow that.
Hope this helps.
Best,
Dan.
