You would probably do fine with either of those. Looking at what you get for the extra $45 for the CS2, adjustable stem, chainguard, upgraded rear derailleur and tires, I'd probably go for the CS2. Or if you really like the white over the blue, the shop may be able upgrade the rear derailleur on the CS1 for about that much, maybe less. I'm not familiar with the Shimano "we're not going to even bother naming this model" derailleurs but I would be wary for anything other than very occasional riding and it sounds like you're looking to do more.