Ceramic or porcelain tiles for underfloor heating

[Crawford1206]

We have arranged for underfloor heating to be installed within a kitchen. The builder doing the work has advised that porcelain tiles are best. They take slightly longer to heat up but retain the heat. Whereas ceramic tiles heat up quickly and get quite hot on the surface.

I would appreciate your comments on the above.

Thanks

(Btw - I beleive the best flooring would be stone/slate but it is out of my price range)