This is speaking in regards to what's currently available or easiest to find:
When it comes to accuracy, the best headpieces are Relicmaker's, as one was cast off a production piece and the other was sculpted with reference to the original. The gold plating is different than the originals but looks great with a thin wash of dark paint. The only "con" I've found from personal experience are the crystals, as both sets of crystals on the headpieces I own have a bit of damage to them.
Otherwise, there's the AcmeArtifacts/ReplicaProps version, which is lower priced but is not entirely accurate in the sculpt. However, it does appear to have a bit of lineage to an original and is a great value for the price.
If you dig deeper into the past, you'll find versions from:
Acme Magic Co - probably regarded as the most accurate for the longest time
Indy Magnoli - hand-sculpted with a thicker neck like the original
Relic Raider - has a larger sized sculpt than all others
Redfour - made of bronze, if I recall correctly
The AcmeArtifacts and Redfour versions (along with a Cinema Replicas version) appear to be variations/casts of the Acme Magic Co version, with differences in the materials used to make them. Some are made of bronze, others are made of pewter and plating.
Here's an old photo with a bit of comparison; note, Relicmaker's versions are not included: