Ordered a SS with classic buckle, but concerned that it may not withstand sweat and abuse from a heavy workout. I would prefer to stick with a single band... Is the classic versatile enough, or is the sport band the way to for a single band?
I actually used my SS with Black Classic Buckle at the gym for about a week (I go to the gym daily) till my Black Sport Band finally arrived yesterday, and I found no noticeable wear nor degradation to the leather of the my Classic Buckle band. It actually feels about the same as when I originally received my Apple Watch, just the leather's finally softened up a bit (it could also be because I don't sweat as profusely at some others when I work out. I run and lift weights afterwards).
The leather Apple used is quite durable. I used my Moto 360 with leather strap at the gym once (was waiting for the steel link bracelet) and the Horween leather lost it's soft-touch, suede-like feel immediately after a day.
Although, like the others have pointed out, I wouldn't recommend using any leather band at the gym long-term, a few trips to the gym doesn't appear to affect it in any negative manner. Definitely invest in a sport band if you intend on doing a lot of high intensity workouts.