I have also used a SQR Slim for three years and love it. It's the only bag I know of wide enough for a laptop computer, if that's important to you. Otherwise, it's largely a matter of whether you want the side pockets or not as both are supposed to be the same capacity. I used the D-rings to attach my wedge bag with my spare tube and bike tools to the top of the SQR bag, so it sits just behind the saddle; if I'm riding without the SQR bag I remove the wedge from the SQR bag and attach to my seat.
Re: papers getting mangled, just put them in a manilla folder, flat envelope or something before putting in the SQR bag.
Oh, and I attach my Cateye TD-1000 to the back of the bag, like they show for the Tour bag on the webpage.