I have / use both. Dummy rounds for function and safety testing.
Also use dummy rounds for dry fire. I have a laser cartridge and a "universal" muzzle laser for dry fire practice, too. It depends on what I'm doing.
For snap-caps / dummy rounds, I've tried many. By far, the best are "B's Dummy's."
B's Dry Fire Snap Caps, Dummy Rounds, Gun Safety, Training Rounds, 3-Gun, Cowboy Action, Highest Quality, Best Value, Most realistic look, weight, and feel.
www.dryfiresnapcaps.com
These are all my own pics from a review I wrote up on my forum.
They use actual brass and lead bullets. So, the weight is pretty much identical to real ammo.
They don't chip up and wear like others (made of plastic or aluminum).
Once they get boogered up like this (where are the chips going??)... There can be problems with consistent extraction.
Perfect for SAFELY function testing at home after disassembly / reassembly or installation of parts or accessories.
For 9-mm, I ended up getting another box, so I could have one in my range bag and another for my bench. They are available in a variety of color combos.
At the range, they come in handy for "ball & dummy" drills. Great way to work on diagnosing and correcting a "flinch."