Hi,
I have both Ikea products and am using them for their main purposes.
The Kolon is a very robust material, as expected. It is almost clear, has some texture on upper side, and smooth on the other. If cut by some kind of machinery, I'm sure it will serve well as a template material, but I'm not sure if clean edges could have been easily obtained by hand cutting. Ikea site says both PET and PU for the material; Anyway, it's a hard wearing material.
The Skvallra is made of a more flexible and less robust material, assumably polyethylene of the low density kind. The site says both PE and PVA. Confusing. It also has texture on one side and smooth surface on the other, but less transparent than Kolon. Being a softer material, it is definitely more suitable for hand cutting, though. As a whole piece, it loses its flatness a little by time but when cut into smaller pieces, I don't think that would be a problem.
Btw, I suggest laser cut clear acrylic for template material, especially if online service is obtainable. I haven't used the material as template for leatherworking yet, but I can't see why not. Apparently, this method requires some CAD involvement.
Regards,
Erhan