The MSI HAWK is a factory OC'ed card and would give you better performance, while the Sapphire is just a poor old reference card. So cant compare both of them I suggest the HAWK on this. If you are not too comfortable with Oc'ing yourself.
the 2 fans could help with cooling. pci-e 2.1 vs pci-e 2.0 makes no difference, 2.1 has compatibility issues with 1.0 pci-e slots though. the 25 extra core clock could be easily reached with overclocking. the memory clock of both are 4800mhz.