Here's the view of an older hot rodder - from the street level.
The point of the discussion is really which motor can the average guy build to get horsepower. Mod motors are factory motors, and it's the only choice the factory has to race with or make cars. That's based on 1) cost 2) emissions. It's what Ford decided it needed to work with going forward. These cam motors do well in factory hands, and yes, make a lot of horsepower - with a highly trained and degreed engineering staff behind it.
For the guy on the street - it's much different. He hears about his neighbor's truck spitting plugs out the block, the intake leaking
antifreeze, the plastic manifold, and lord help the guy who flips off the cam chains - there's no index marks to time it back again, it's a $350 min machine shop charge locally. Those in the know still have to buy the $150 kit to clamp the cams down.
It Is Not User Friendly.
Look at the other side of the VS - a Dart block? We're talking aftermarket support so deep you can pick and choose non Ford blocks to whatever level of horsepower you need. All it takes is money, whether in cubic yards or a credit limit. What you can get is a 427 - from a 351W. It can be a crate block built for racing, with seriously cast and hand ported heads, plus all the allied parts specifically developed, and most of them waiting on the shelf.
Mod motors don't have that depth of parts or support on the market. In a large degree, it doesn't exist because the cars that debuted with them came at a time when severely restrictive emissions laws were in place, and very few could do much with them. But - the Windsor motors go back to the '60s, and so do the cars that had them. All those owners aren't moving up to mod motors. There's no reason to, unlike the pre 63 owners who largely dumped the Y block back then, and even lately, the FE's.
Mod motors are what you are forced to buy in a car to meet draconian emissions standards, Windsors are what somebody builds to have fun at the track, strip, cruising, at shows, etc. because HE can screw it together and not pay a mechanic or buy expensive tools.
I'm glad I'm not stuck with a mod motor or a car that's required to use it.