I think the large versus small is more a question of how you carry the knife and if there is any real or perceived problem with other people where you use it. When I worked in an office, the small didn't raise any eyebrows, but the large sometimes did. It helps to open them somewhat slowly, and not snap them open in front of your manager. (oops)
If you use the clip or a sheath, it doesn't matter which size, so I would go with a large. If you carry inside your pocket without the clip, I would say the large is too large for loose carry, and go with the small. When I was looking to buy my first Sebenza, Chris (who's tall) showed me his EDC, which was a small, carried inside the pocket. I said that I thought a knife should be large enough to be an emergency steak knife, when encountering dull knifelike devices in restaurants and friend's houses. Chris replied that we mainly use the first two inches of the blade anyway, and that he found it an adequate steak knife. (and related an amusing restaurant story I won't bore everyone with)
Of course, my ultimate decision was to buy both large and small regular Sebenzas. Bridget was a good saleswoman, and left handed versions of both happened to be available. So I guess I'm not the best person to call for Buyers Anonymous.
As for durability, the micarta is the best, but for woods, unless you carry hard items in your pocket, your hand will wear them all about the same.