Go for the Mustang because at lease it is a Ford product and the two others are GM and FCA junks. 

Challenger with the 5.7L V8. Old motor that is known to be reliable.

Mustangs after 2018 are junk. Ford switched to plasma lining the cylinder walls and they drink oil, tick, bang, etc.

Camaro is just getting by on GM's nearly empty parts bin. Valve spring issues, transmission problems, etc.

This is the one area where I would actually go with the Chrysler, and I'm not saying it is built well. It isn't. But it is the least crap of the three.

Subaru BRZ would be my speed. 

In terms of reliability, neither of them unfortunately.  If you get one, make sure it is under warranty the entire time then get rid of    before the warranty expires or just lease it and get out of your system.

I love the Challengers. But, from the research and owner feedback, they have notoriously bad electrical systems. I’ve always heard Scotty say that six cylinder mustangs are the the way to go if you want an American muscle car. 

If you want a reliable sports car you might want to look at a Miata or Civic Type R. 

All I'm gonna say is that Dodge is keeping the old-school American Muscle tradition alive. Their V8 engines are better than Ford's. And their V8 lineup is specifically made for performance with their launch control, sport modes, performance gauges, etc. So if you really want to experience muscle, Dodge is the way to go (only the V8s). You're gonna have tons of fun with it compared to a V6 Mustang Scotty recommends buying. Plus, Dodge is using those super reliable ZF transmissions now, and they can really handle the V8 power. However, I do agree that they have electrical issues, but their engines are built great.

I like the older model Mustangs, but I haven't been very intrigued by the late models models...especially when they released the ecoboost version.