I think if you looked, you'd see Wilwood has quite a bit of coverage out there. They've been around a long time in both the race and street market. We certainly view them as a business competitor, they move a lot of product.
Take a look at all the variables and make sure you're focused in on what's important to you and how you'll be driving. I'll touch on some of the points of our StopTech system, which may give you some questions to ask in comparison.
First off, we talk a LOT about "Balanced Brake Upgrades". By this, we mean maintaining the proper balance between front and rear brake torque so the car will have optimal brake balance with the stock master cylinder. If you're equipped with a dual master, you have a lot more flexibility for tuning the balance. Make sure the calipers have the proper piston area for your vehicle, and if you have other than stock rear brakes, you should let the brake supplier know so they can assure their standard kit will maintain the proper balance. Here is a link to the Technical page of our website where we have several articles posted abour brake balance and upgrade issues: StopTech Technical Page_White Papers
StopTech offers a 2-piece floating hat & rotor assembly. A floating assembly is less prone to distortion under extreme driving conditions. A one-piece rotor can do the job very well to a point, but on an open track under competitive conditions, a floating set-up helps. Here's a link to an FAQ detailing floating v. fixed hat & rotor assemblies: Fixed v. Floating Rotor Assemblies
As far as long term cost of ownership, research replacement rotor costs as well as pad availability and cost. For rotors, I think Wilwood will be pretty well priced compared to Brembo or StopTech, but take a look to make sure it's an apples-to-apples comparison in terms of rotor design and performance. I think there's pretty good coverage for pad compounds for any of the Brembo set-ups, and "decent" availability for the 6-pot Wilwood. I think the 6-pot will have more track than street pad choices, but you should be able to get that info. We use a very common Porsche pad shape available in just about any compound from many suppliers.
See what all is included with the kit in terms of pads, stainless lines, all the hardware, installation documents, etc.
If you have any specific questions about StopTech, don't hesitate to ask. You might also call the others and see what they have to say and how comfortable you feel dealing with them, that's important as well.
Good luck on your decision-