As others have mentioned it depends on your use case and budget.
If you want a collectable that won't be shot a whole lot, one of the original preban FN made FALs are at the top of the collector pyramid. That said most of the imported FN guns have cast receivers with a reduced service life over forged and if you break something you will damage its value replacing an OEM FN part with something aftermarket, so the original FN guns are not the best option as a high volume shooter.
If you want one of the most robust and well built FAL pattern guns made IMHO, get one of the Springfield Armory imported SAR48s that were fully manufactured by Imbel. The SAR48s are fully forged type 3 receivers and the entire rifle was manufactured by Imbel using only their high quality forged/stamped components.
If you are on a budget and need something that you can shoot and has a warranty and is commercially available than DSA is your best bet.
If you want to scrounge up a nice parts kit, an intact barrel, and an unbuilt Imbel receiver (or older forged DSA) you can have a really nice gun built by Mark at ARS (which is probably better than a run of the mill commercial DSA) but be prepared to invest a lot more time and effort to get it built vs. just pulling out your credit card and buying a complete DSA unit from Atlantic, etc.
I have two FALs both on Imbel receivers. One is a semi auto built on an Imbel receiver with a Austrian STG-58 parts kit and the other is a Springfield/Imbel SAR48 converted to a machinegun SA back in the 80s, that I then further converted to a DSA OSW.
Since we are sharing pics.
SAR48 / DSA OSW FAL on top with an AR10 (Colt LE901) and HK G3K on the bottom for comparison.