I wouldn't use the advertised boost clocks as a deciding factor. Non-reference 980Ti's always boost higher than advertised numbers out of the box, and then they all overclock beyond that. The advertised boost on mine was 1279mhz but it was about 100mhz more than that out of the box, and I overclocked to 1.5ghz with ease (note: I'm talking about the boost it actually runs at during a game or benchmark, not what GPU-Z reports).
I would use other things like cooling performance/noise and warranty as your main deciding factors. For example, for someone like me who lives in Canada, I want a brand that has RMA centres within Canada so I don't have to ship it to the states (takes longer, costs more, and potential brokerage fees & taxes on return shipment). That's why I went with MSI in my case.
I know EVGA has a good reputation for warranty related stuff (unless something has changed recently), but they were out of contention for me since I'd have to ship a bad card out of country for any service. Asus has Canadian RMA but when I bought mine no one had the Strix in stock.
When you're dropping this much money on a component, warranty service is pretty damn important. Oh and FWIW, my MSI Gaming never thermal throttles at my current overclock. Cooler works well.