The glass screen is much easier to scratch than sapphire so whether or not this will be an issue for you will depend on your tolerance for minor scratches and how likely you are to scratch the watch. I work in a laboratory and I knock my watch against stuff all the time. The screens on my S0/S1 aluminium Apple Watch have quite a number of scratches. I have had a S2 SS for a year now and the screen is flawless. There are some tools/abrasives in my lab that can scratch sapphire, so I am especially careful around those.
As for the body, the space grey (my S0) easily reveals the silver aluminum underneath if you manage to scratch it (as I have mine). Obviously, this isn’t an issue for the silver variant. As for the gold variant, it looks very similar to the silver anyway so it isn’t obvious even if this happens. The main issue for the regular SS is that it is highly polished, so any tiny scratch becomes obvious (though they can be buffed out). In terms of durability, the SBSS is obviously the best...