That's a tough choice. I have the saleya Azur in MM and I love it but I recently got the palermo gm because I wanted more room. I like them equally for different reasons. The palermo because it is more versatile with the shoulder and body strap but I like the azur saleya as it's a nice size and colour for the spring/summer.
I think which ever you decide you won't be disappointed as they are both great bags and if in doubt buy both!