Purple Medicrystal vs Tan Thermogem mat. Both have PEMF and Photon features.

The Purple Bio Magnetic PEMF Photon amethyst mat with additional PEMF and Red Light functions contains a thick layer of tumbled 3-10 mm natural amethyst crystals, together with 1.2" (30 mm) disk-shaped agate stones, all affixed with mesh fabric and without glue. 

The purple MediCrystal mats with amethyst and agate disks are the best we have with PEMF and Photon functions and are the most expensive. 

These mats have crystals from edge to edge, while the tan has PU leather lines along the sides. 

Tan ThemoGem 3 Gems Bio Magnetic Photon Mat and Purple amethyst agate Bio Magnetic Photon Mat both are featured with PEMF and 660Nm Red Light Functions. 

This mat comes with approximately 50-60% of tumbled natural amethyst crystals and 20-25% of each natural (non-ceramic) black tourmaline and green jade, all obvious and affixed with mesh fabric, without glue, by an artisan sewing method. 

These mats also have several lines of 1.2” (28-32 mm) ceramic tourmaline hexagons of the famous Korean NightShine brand.

They may be supplied with the F-series controller or with the H-series controller, each more advanced than the L-series Controller for the Purple mats. 

H-series have a built-in safety function that decreases the temperature to 45°C if it has been higher than this for 4 hours. It is a good protective feature if one falls asleep on the hot mat.

The tan MediCrystal mats are a little cheaper because they are built with approx 40-50% of amethyst, and the rest is other cheaper stones such as tourmaline, jade, etc.

I am sure you will be happy with an option; just over which stones you prefer to have on your mat.