Are they as safe to carry as one with a hammer?
Safe to carry?, yes. Safe to use?, maybe not.
The problem is not in the holster or that it is a striker fired pistol, the problem is in the trigger and your trigger finger. Yes, everyone will tell you to keep your finger off the trigger (LOL), like that will ever happen. In a stress situation where you only have seconds to decide what to do, your trigger finger will by instint find it way to the trigger to be ready to shoot. Now, striker fire pistols without a safety will NOT give you that half second to change your mine about shooting. If you have to manually remove a safety before firing, it gives you that extra time on your sight picture and that what you think is a good shoot, is in fact a good shoot and not a mistake. (police departments are finding officers with Glocks shooting suspects with cell phones by mistake.)
Striker fire pistols have a lighter and shorter trigger pull than SAO or DA/SA pistols. The extra quarter of a second it takes to release the safety gives me the time to make sure that this is what I want to do. (No way to take a bullet back after the trigger has been pulled.)
The great sages that tell you to keep your finger off the trigger have never been in a gun fight and had less than three seconds to end the threat. (finger off the trigger just does not happen in real life.)
So are they safe to carry, yes. Are they safe to use, I DON'T THINK SO. But that's just my opinion.
Jim