They are totally different. You have cable heating and then 'ribbon' heating. Cables perform much better and can be installed much easier, especially on a mat.
I'd checkout
Electric Underfloor Heating UK DIY | Homepage for Handyheat and
Online Electric Underfloor Heating Specialists too.
Don't worry about the elctromagnetic fields, they're only really a concern with single core cables which need connecting to the stat at the start and end of the cable, twin core only needs to be connected at the start of the cable or cable-mat.
Plus, it's apparent that the frequency the elcromagnetic fields emit at are not on the frequency which effects living beings anyway, even on a single core. Or so I heard.
Elektra cables are good but were always too pricey, similar to Devi.