Prada!!! I had the same debate before, and I ended up with Prada. It has more color of choice and so much cheaper than Chanel. I know this is Chanel forum, but I have to honest that I love Prada luxe tote so much more than the Chanel cerf tote.
Cert tote of course, its timeless and so classy, simple yet elegant. It has few zipped compartment and additional 2 compartment on the front and back of the bag, how thoughtful and convenience to use this bag. Nevertheless, I believe you should get a bag that will suits your need, lifestyle and style. Cert is more of a hand held bag, though it comes with a shoulder carry strap. It does look more chic hand carry. Good luck!!
I would personally get the Cerf. Right now, I feel like you have to be careful with Prada. Certain bags are ok, but others, I feel like the quality has really gone down hill right now. The Saffiano totes in particular. I am not a fan of the glazing and I feel like it looks a bit cheap-y. There will definitely be cracking with the prada glazing on the saffiano tote.