I do have the GST, I hate it lol, but I also have a lot of flaps so I know what you mean about the leather. Lately the classic Cerfs weren't as nice as they used to be. They looked dull and a softer black than even just from a few years ago. However, I would love to test both together and see which is heavier, but it seems the classic version is now goneEveryone says it's been discontinued…is that maybe not true? Are there still some out there? I got my seasonal one at Saks and I know they for sure didn't have the other.
Hi again! By the way, if you are using is casually as an everyday and don't need to put much stuff in it, can you find a way in your to love the GST?

I love love love the GST and it's my everyday bag that I rotate the colors (I have several of them). The cert tote is my travel bag.
I like the GST a lot more as it more classic Chanel (the quilt, CC logo), and it can be used almost everywhere.
I know some people find the cerf tote formal, but I'm the opposite. I find the cerf tote a bit boring and more like just a big tote with an open hole. Don't get me wrong... it's my work bag when I travel, but I only purchased it for that purpose (I travel a lot).
My true love for a tote is the GST. It has the center zipper which you can zip up. The side slots are open so you can just grab stuff when you need to. I actually tried to use my cerf tote casually but it annoyed me. The cerf tote has the detachable tote, but it is totally annoying... it never stays attached, so I just took it out. But then it's one big hole, so you have to use little bags like the LV Toiletry bag so your little items don't fall out or are just scattered all over the bottom. I don't carry much, but the stuff I carry is small... compact, lipstick, credit card holder... all these fit perfect in the GST center zip pocket, but in the cert tote, it's like a few pieces in a big hole. And you think you can just grab things, but the center cross-magentic strap is a pain to open and close.
Anyway, something to think about. I would not use the cerf tote as an everyday bag as I find it annoying. That's just me.
So.... this is just my two cents I wanted to share with you in my uses for the two bags... the pros and cons that I find.
Good luck!