All the answers to the contrary which you are going to get are wrong, wrong, wrong.
By far the best version is the original theatrical cut. The international release is very slightly better (one minute of "scary violence" is cut from the U.S. release), but either that or the U.S. release will do very nicely. This is the only version with Ford's voiceover, which is absolutely essential to understanding what is going on. It also adds tremendously to the noir feel.
The only way I know for sure to get this version is to get one of the multi-disc sets which include the "1982 theatrical release" (the 5-disc blu-ray set is a slam dunk). You can also get it on cable, but I doubt it is the only version circulating on cable or streaming.
All other versions (rare original workprint, 1986 U.S. broadcast version, 1992 director's cut, 2007 final cut) are CRAP in comparison.