Glad to hear that you were able to go to Saks and try on the Disco. I have 3 discos and I love using them. The disco can deceivingly fit a lot, and the strap is sturdy. My husband calls it my magic bag, lol. Inside, it can fit my cardholder, a compact wallet, sunnies inside a fabric pouch, hand sanitizer, a pack of tissues, lip balm and keys, plus hubby's sunnies too.

There is a disco thread (clubhouse) and you can find a lot of information there.
The only con I can think of (which the wearer has control of it, by the way) is that because the bag is lightweight, it can flip over (turn upside down) and the contents will fall. It happened to me once, I didn't zip it close and when I got it from the car (grabbing the strap only and not the body of the bag), everything spilled. Lesson learned, haha. Again, it's something you can control and just be mindful.
I also considered the trio before. I wasn't able to try it in store though.
I really liked the small by the way when I tried it on. The size was perfect but I also had an issue with the strap. Because the strap is adjustable, the look of the exposed snaps bothered me a lot so I didn't proceed with the purchase.
Good luck with your decision. Are you looking for a specific color? Can you hold out for a sale (spring and fall)? I was fortunate enough to purchase 2 of my discos on sale and the other one I purchased from the outlet store. Hth

!