The PSL client was intended specifically for the PSL. The SWLACC client, despite the name (which is kept to avoid confusion), is now a full time anticheat client.
And yes, about features. There are, and they aren't worthless.
Client-side demos.
Extended scoreboard with extinfo (you see the right accuracy even you don't attend a round from the beginning).
Generally better performance than the vanilla client, because it is built with a more modern compiler and with up to date libraries, which are linked statically. libjpeg is replaced by libjpeg-turbo, and the speedup in map loading is noticeable.
Have a look at http://swlacc.pisto.me/viewtopic.php?f=1&t=4 , under "Reference".
I don't know what is sauerx-mod. But differently from the time when Markku was maintaining this mod, the point of the SWLACC is not to detect what mods (and possibly cheat mods, you know what I am talking about) you have used in the past. On a side note, this mod is a completely different code base.