Mike,
It's a UK rag that I don't think you will get in the US. It covers 11 pages, but much like women's magazines that tell them how to loose weight and get a better life over 20 pages, it can be summed up in a few sentences:
1. SL's are 'classic' cars. (Apparently this includes the wretched post-107 SL, whatever model that thing is). This includes the SLK, although the original 4 cylinder 230SLK compressor (which I owned) is largely crap, so don't bother. (I agree).
2. The older the car, the better. This means that the 300SL gullwing is top of the heap. (No S&*t!). Work backwards from there.
3. Some SL's are more desirable than others. Thus, of the 113 heritage, the 280 is deemed 'better' than the 230. This is due to 'improvements' made over the years, such as all-round discs, drilling out a 2.3 litre block to a 2.8 and so robing the engine of its ability to cool itself, etc.
4. W113 280's attract a significant premium over other SL's. (This turns out to be 10% later on in the article and I suspect it has a lot to do with what Chelsea Classics charge - this is a UK company that sells more 113's than anywhere else in the UK; they are only really interested in 280's. They are sort of market makers in the UK, or London, at least. They don't have a great repuatation. 'Nuff said).
5. All SL's will appreciate with age, and the 107's seem to be the best bet for now. The 500 SL is the best within that range, and the 450 SL stinks. Or so they say.
Basically, it's a 'get six pack abs in 5 minutes whilst drinking more beer' article. If you've read my 5 points to a more successful motoring life, you've missed: nothing. And you've saved the equivalent of $5 cover price.
Cheers!