Neither are particularly safe: you should really have someone who knows what they're doing on set if you're using blanks. I don't know about Seattle, but in the UK the law requires blank-firing replicas vent the blast out the top of the gun for safety reasons and that means they look crap on screen.
Personally we use non-firing replicas and add muzzle-flash and shell cases in post... if it was good enough for Peter Jackson it should be good enough for most people on low budgets .
btw, i believe my weapons armorer quoted something like $20 per blank if i wanted to use real guns. That doesn't include cost of gun rental nor the day rate of the required licensed armorer who must be on set...Go Digital!!
Never give an actor a real gun. I used real guns in my first feature film. For blanks I handloaded primers only into empty cases. This gives you a nice little flash you can enhance with a big bang later and is much safer than a more powerful blank with wax or wadding. That said, one actor who had no experience with guns managed to put himself in a dangerous situation anyway.
If you must use real guns you can get a primer seater for under $40.
(Note the primer trick will not work with auto's. There is not enough gas generated to recock the gun.)
I use airsoft guns now. A big bang cannon (Still Available Online) is a great way to make muzzle flashes in almost any direction.
For bullet hits and blood shots without squibs check out How to Do Blood Shots without Dangerous Squibs
for any student or newbie, i strongly recommend hiring a professional for assistance with this. On the shoots I've worked on with real guns, there are a ton of precautions taken on the set.
Only the armorer handles the firearms. When he takes them out of their cases, the AD announces to everyone there are live firearms present. The guns are handed to the actors right before the take. Once the director yells cut, the armorer runs out to take them back from the actors. NOONE else can handle them.
Even if you own your own guns (not uncommon in many places in the US), do not think it's a small issue having them on set.
The two main advantages of purpose-made blank guns over real guns with blanks, if you really want to go with blanks:
Legality. Not legally firearms, so can ship to your home, be handled by an actor who can't legally be in possession of a firearms (depending on your local laws, anyway), can be used on school grounds or elsewhere they don't want real guns, etc.
Can't chamber real ammunition, so no chance of a stupid mistake like on Rust or The Crow, both of which partially happened because of people wanting dummy rounds in their gun.
The main disadvantages:
Can't load dummy rounds, so can't show it being loaded or unloaded.
Much less selection
Usually crappy quality control... often they suck
Ejected casings are obviously blanks in close up or slow mo (either a crimp or a plastic cap at the end)
No trademarks or other things to hold up in closeup (not your hero prop version)
Still dangerous, but people might not treat them as such because 'they're not real'
But yeah, there are plenty of other viable options besides blanks, so choose carefully, and have someone who knows the field help you choose.
-Kevin Inouye www.fightdesigner.com