I just picked these two knives up from the PO. Here are my impressions before I actually use them.
The S1 is smaller and lighter. The handle is smaller and feels good and I imagine it to be a good knife for smaller chores and delicate work. But this is still a tough little tool as it's practically as thick as the SRK.
The SRK is longer and heavier. Probably better at chopping than the S1 but the blade is still good for slicing. The handle is slighter larger but I have medium hands, long fingers...so I'm able to adapt to smaller and/or larger handles.
Keep in mind that the S1 is much more stain resistant than the SRK, even though the SRK is coated.
Personally, I would carry the S1 and then an HI Khukuri as a larger chopping tool (if you need one).
But if you're looking for a deal then Cold Steel will still have SRK *seconds* for sale until the end of January (call to confirm).
I picked up one for $30! Great deal! The S1 is more than twice that price. I couldn't find anything wrong with the *second*.
These are my views as a relatively new knife knut. Hope they help.
Burton