There is a R1 version of Saw, released in Feburary 2005, that features the same extras as the R4 version, but differs in a couple of other areas.
The R4 version misses out on
By all reports the DTS audio track is brilliant. We may see this track on a possible R4 special edition in the future. But, until then, I'd stick with the R4 version. The Dolby Digital audio track is quite outstanding and the PAL transfer is superior. However, if the DTS track and subtitles are of great importance, then you might want to consider the R1 version.
The UK R2 market has two releases, the cut version and the uncut version. The latter is the choice selection if you want the untampered-with edition.