Both the wacker P12 and the radio shack thermal paste are very high high quality products. As are probably dozens more on the marketplace.
The P12 and the Radio Shack products are made from a silicon grease vehicle with zinc oxide and silver added as a conductor.
The P12 has a conductivity rating of 0.81 W/mk and a working range of -22 to +392F.
The Radio shack product (made by NTF electronics) has a conductivity rating of 0.80 W/mk and a working range of -40 to +400F
Neither product is made specifically for aircraft engines, but for electronic heat sinks.
Both products are almost identical in specifications and both will do the job. The whopping big difference is the price and availability of the products.
An added extra is that they both work great in preventing sunburn when smeared on your nose. Believe me, I've tried it.
Bill.
