I've had a large for about 3 years, and I just had a chance to work with a small. The small is sort of a beautiful miniature of the large. The real power of the Sebenza design and engineering - its sheer strength - can be fully appreciated in the large blade only IMHO. Concerning clothes, I have never found the large to be a problem in jeans or any other pants (I carry in the waist band) made at least in part for the outdoors. It is indeed too heavy for the lighter fabrics of a lot of city and more formal clothes.
Now that I've said that, I will say this for the small...
1. It is a better paring knife, but that was just about the only task I could think of at which the smaller size actually made it better while in use.
2. When NOT actually employed in cutting, the smaller size has several advantages. It is very much lighter and thereby fits better in "city cloths" and other more dressy settings. A customized version would certainly make a great "gentleman's knife", though the plain is a bit, well plain, for that role. When deployed, it doesn't register so dramaticly with the "city folk." This of course is true of most smaller folding knives, they don't have to cost $300.
Of course if I were stranded and in my city clothes, I'd certainly rather have *that* small knife than any other, but for most of the things I actually do with a knife while in city clothes it hasn't quite enough bang for the buck IMHO.
My recommendation therefore is get the large unless you just are never out of your city cloths and won't be able to deploy a knife as large and heavy as the large one. If that is the case, then the small one is certainly an engineering marvel, so if you can afford it, go for it.
On a side note, the new style clip (avail on large and small I'm sure) is really nice. Works exceptionally well.