Yes, I think in theory it will so low you down, but also training will have a lot to do with it. I suspect if you train with the thumb break holster (using an unloaded gun) and develop muscle memory which makes drawing the gun automatic you should be fine.
However, as I said earlier unless I specifically felt I needed some type of retention device I would get the holster without the thumb break.
A major source of objection to a free economy is precisely that it ... gives people what they want instead of what a particular group thinks they ought to want. Underlying most arguments against the free market is a lack of belief in freedom itself.
- Milton Friedman