I'm in the market to purchase a new test kit for Ca and KH. Considering either Salifert or Elos.

Recommendations?

I think they are both really good, top of the line. I would go ELOS.

Out of the 2 you listed i like Elos. I actually prefer Seachem for KH because you can also test for Borate Alk. I don't think the other kits do that.

I used Salifert for years with great luck. I recently switched to Seachem because I couldn't find the Salifert kits in stock anywhere.

The Seachem CA is much harder to use (more steps) than the Salifert.

You can't get much easier than the Salifert KH test...