If you track regularly you probably knew about the benefit of 6 piston vs. Depends on who makes it how it works with the car etc.
Dinan By Brembo Replacement Brake Pad Set Bmw 1 3 5 6 Series M3 Z4
6 piston calipers vs 4 piston. Compare that to one of those really long 6 pads found in a huge 15 rotor set up. A 12 brake kit with the 6 piston calipers cost about 300 more than a 4 piston kit. They are almost always fixed position calipers without a bracket similar to the 4 piston design. The stock m3 caliper single piston is probably nearly as good as many 4 piston aftermarket calipers. 4 pot calipers means that the brake calipers are holding 4 pistons. Different types of calipers the thing that holds the pistons themselves will hold different amounts and types of pistons.
The 4 piston calipers are going to do a very similar job at distributing x amount of force as the 6 piston design. The calipers themselves are made from a variety of materials steel and aluminum being the most popular steel for durability and aluminum for weight. Thats because the pads are what 35 to 4 long. They actually have a lower profile than the dynalites so they will fit inside a 15 wheel with more clearance. 6 piston calipers usually feature 3 inboard and 3 outboard opposing pistons. It fits the same bracket as the regular dynalite 4 piston caliper.
To answer your question i wouldnt pay a premium for a 6 pot caliper over any other caliper unless performance was dramatically better. Some say they arent happy with 4 piston stopping power and they shouldve gone with 6 piston. On 6 piston calipers you will usually be able to see the outlines of the 3 pistons on the outboard side of the caliper. Depends on a lot of stuff. 4 piston so i would think you are not track junkie so i would say stick with 4 piston which will give you more than enough stopping power.