Both are very good guns but, based on what you said I would go with the CZ as it is better suited for the HD role you want your firearm to play.
What you said about revolvers ("just need to pull it out of the locked box and I'm good to go") is not true of the Ruger Blackhawk because it is a single action revolver. Unless you plan to store it cocked (which I wouldn't advise), then you need to pull back the hammer before you can get a round off, and you need to repeat this process for every shot.
I would not recommend a single action revolver for HD for this reason.
However, if you may consider other revolvers of the double action type (Ruger Redhawk or make/model), then it is more a matter of personal preference. The revolver is simpler to operate (consider a dud round for example) but a semi-auto generally gives you much greater capacity. And is usually quicker to reload, should you need to.
BTW, I would not worry about "mag stress". It should not be an issue. This subject comes up around here occasionally and I've never heard it be an issue. I personally have kept fully loaded mags in my pistol for months and months and it has always functioned when called upon. I'm pretty sure everyone else will say the same. Also, you will want several mags for your gun, and you can change them out periodically.
Hope this helps.