Adhesive selection making my head spin!

[SuperPav]

I've got about 70sqm of 15mm limestone flooring left to lay.

 

Laid about 8sqm already in the utility and behind kitchen units, that was done with a combination of Keraquick (white) and Keraflex (white). All went well.

Stone is being laid over Mapei decoupling membrane (over heated concrete slab).

 

I now need to buy 15-20 bags for the remainder of the space, so to lay 70sqm of membrane + 70sqm of tile. I am not professional so don't work quick, but don't actually mind working with the rapid set stuff as I mix up a half bag at a time and keep going every 20 minutes or so. The slow set stuff is easier two work with but I do find that the tiles move so much that spacing them (keeping them tight to each other) is almost impossible as they're like jelly. And as we're living/camping in the house, being able to use the floors quicker is a (albeit very small) convenience benefit.

 

 

I've been very happy with the Keraquick stuff, so if money was no object, I'll just get that for everything. 

 

However, there's Mapeker Rapid Set white which is approx 15% cheaper, and on paper is exactly the same??? And then there's the "generic" Mapei Rapid Set S1 white, which is 30% cheaper than keraquick. I cannot for the life of me work out what the difference is.

 

What am I missing? 

 

Should I get some slow stuff and cheap grey stuff for the membrane to lay a strip, and then use the expensive white keraquick for the tiles only?

 

Or should I just get keraquick and stop worrying about it...