If I could afford something expensive it would probably be a plainer Coach bag. They seem really well made, and they have a lifetime repair warranty. I would stay FAR away from any logo thing. I don't think I would get a knock off of a currently fashionable shape, like a faux-Birkin, because the fad will pass, and while a real Birkin is a lifetime investment, a knockoff won't be worth the leather it was cut from when the fashion passes.
I would not get coated canvas. It gets icky looking right away and doesn't clean well, and it is not like you can just bung it in the washing machine, like you can with a plain canvas or denim bag. I would go for a sturdy leather, not a slouchy one like the MiuMiu, but then again, I only ever have one bag at a time, and use it until it is worn out, therefore sturdiness, maintainability, and durability are of the essence to me. Ditto a style that doesn't go out of fashion, since I will easily tote a bag around for 5-6 years. If I could afford better quality stuff, it would probably be for even longer.
I like dark-colore (black or brown) smooth leather, because you can clean it with saddle-soap and touch it up with shoe-polish when it gets shabby.
I like the Marc by MJ one, but I would have to get it in black or brown if I was getting one. It looks like a good all-arounder. You could carry keys, snacks, wallet, novel, sunscreen, camera, ect. in there, it looks like.