Caviar leather is definitely more sturdy and durable - it is tough and a lot less likely to get damaged compared to nappa, which is delicate by nature. However, I find GST too structured and bulky. Very heavy on the shoulder even when empty! I love gaufre because of its suppleness and casual chic. Would vote for the latter any day!
I have both & love both but if I had to choose one it would be my GST, Ive only had it a month where as the Prada Ive had for nearly 3 years & not used that much so looks brand new but I do get more compliments on the Prada & its probably because the leather is so gorgeous & buttery feeling, I bought the Prada wallet to match & used it for about a year & even though its still in good condition there is a bit of wear on the corners, I would vote for Chanel but Im more of a Chanel girl these days.