I've enjoyed watching this thread develop. Now I'll throw my 2c in.
I like Fords and have owned a few (5 so far). I've also owned Holdens, Suzukis, Renault, Mazda, Land Rover, VW, Jaguar. I try to judge each car on it's own merits (some of them were good some were real turds).
I chose to go the LS1 at a time when I could have used a Windsor motor with no rego issues. My choice was based on engineering and design rather than brand loyalty.
Some of the things I liked about the LS series versus the traditional choices were all aloy constuction, Un-bustable 6 bolt mains in a deep skirted block (I've never read of anyone breaking a stock crank), All O ring gaskets throughout, compact lightweight and powerful straight out of the crate.
Aftermarket support and development going forward is great and the tuneability of the factory ECU is a real bonus.
Stock they aren't good looking but once you peel the layers off this onion there's a very pretty engine underneath.
As far as the HP is conerned, any of the motor choices listed will make more power than you know what to do with. My mild LS1 is frighteningly fast. I think we get a bit carried away looking for bragging rights and dyno numbers. Truth be told 400HP in one of these cars is a real handful in a street Cobra. Chase more power and you should set up an acount with the underwear department of your local target store.
For a more track focused car you could probably use more power but in all honesty I think the money would be better spent on getting the handling and brakes sorted. As an example John White at the last few Cobra Nationals was kicking everyones butt with a stock Lexus V8 in a very well set up chassis.
I had all sorts of dreams of superchargers and turbos big cubes and whatnot but ended up with a simple naturally aspirated reasonably stock motor. I've got a few goodies to go in it but most are aimed at reliability under stress rather than making power. The change of manifold and 4 barel T/B was a cosmetic choice as I wanted a more traditional look. I don't think it adds much power, It may even cost a few HP. The exception to all this is the cam I plan to install which will wake it up a bit and make all the right noises.
Cheers