I have an SL6 and it's reasonably robust. The switch is electronic so there is a level of parasitic drain. I like that it is small enough for me to comfortably carry in pocket. It is bright and floody. Mine has survived a single drop onto concrete...but I'd say YMMV since it's circuit controlled. The anodizing is thin, so over the years the clip has scratched the surface...clip is also somewhat flimsy but I prefer to carry it lose in pocket. The SL6 also doesn't like longer 18650 cells - they designed the original with unprotected 18650s in mind so Readilast 2900s won't fit (using AW 2200s). Maybe this has changed on the later-arriving SL6S but my Spark SD6 headlamp also has problems with longer 18650s as well.
Because of it's easy pocket carry the SL6 is in my EDC rotation and it's used when camping.
I don't have one to compare, but on paper the SL6 is similar to the Zebralight SC600. Zebralight has a huge following here and many have compared Spark to Zebralight's designs. Selfbuilt has
a review.