Many products being promoted for radiant heat are not independently tested and are not beneficial or in some cases are not what the companies claim. This is a comparison of different products.
These are simply my opinions based on experience on over twenty years of installing and designing over three thousand radiant floor heating systems.

The only insulation to use under a slab is the high density foam board, at least 2", sometimes called blue or pink board, foil products should never be used under a slab. The two layers of polyethylene with Styrofoam sandwiched between them is worthless also, the cells will collapse under concrete and if it gets wet the Styrofoam will dissolve that is why they no longer make boat docks with Styrofoam.     
   I have tested several foil/bubble products and closely examined the so called testing the manufactures claim. They either lie outright or use some obscure engineer who projects R values from his calculations.

Any Pex-A or Pex-B will outlast your house and serve you well.  I do not recommend Pex-C it is simply PE pipe ran through an E-Beam to give it a partial cross linking. The multi-layer Pex, called Pex-Al-Pex some times is actually not Pex but simply two layers of PE tubing with a layer of aluminum between the layers. It is much cheaper to manufacture. It was developed to satisfy the plumbing trade, because of their resistance to plastic pipe, it bends and feels like soft copper. The multi-layer tubing has two problems, if it freezes it will not spring back like Pex does, it becomes over sized and will no longer accept fittings, if frozen more than once it will break the aluminum layer. It will also separate the layers when pulling through the holes in the floor joists on long loops where it must be looped through many holes.

INSULATION, The bubble-foil-bubble insulation is very necessary under any crawl space see page 17 . The only insulation that will work under a slab is the 2" high density foam board. Any product that is less than two inches, contains foil or bubble wrap is worthless as an insulation.
PUMP ZONING, Zoning with a single pump and zone valves is a much simpler and a more efficient system.
EMISSION PLATES, I have done a lot of testing on these, they are totally unnecessary. Raising the water temperature a couple of degrees will give the same output. This is one of those products with no testing but seems to make sense, they do raise the noise level. 
TUBING LENGTHS, Many companies will try to tell you, you cannot install loops of 1/2" pex in lengths over 300'  See Page 11
   Some internet radiant suppliers sell 7/8" Polyethylene tubing as better than Pex and calls it Poly PXC. This is not code approved for heating. They claim it will heat with one run in each joist space. I have had several people call who could not get their home warm enough and several that the tubing simply failed. This is a very cheap tubing and being sold as better than pex. These companies are also promote solar systems that are not going to payout. If you want solar, go to a local company that specializes in solar, they will engineer you a system with proven feasibility for your area.

Many internet radiant companies offer very poor value for their service.

   The main reason I maintain this site is to educate the public so they will have the information they need to help them find a qualified installer and for the installer who is looking for a better way to serve his customer.