I don't see why you'd need a thumb break. Is the idea to have something between the hammer and the firing pin? I would think the manual and grip safeties would be enough, but that's up to you. Go with what you're comfortable with first and foremost. But I would probably choose a Crossbreed Supertuck or similar hybrid.
I just went through the research and holster buying process for my new 1911. I went with a nice leather Galco concealable open-top holster after reading about thumb breaks sometimes dis-engaging the safety.
I bought 3 new holsters for my 1911'a I got a Milt sparks IWB Summer Special 2 from Brownells. And I bought a TactiPac Fusion holster which is great. & I bought the new Reflex OWB holster from Uncle Mike's. Love all of them for my 1911 carry.