Torque...hmmm....
I wonder if I can put a cummins diesel in my 280Z...
As far as weight...well...if you talk about dropping an L28ET in, don't forget the additional weight of things like the intercooler, bracketry, turbo, manifold, piping, etc...in either case, you're going to be adding weight to the car...however...
Don't forget that the 350 will neutralize the weight of the car and lower the center of gravity...the amount of weight isn't as important as where the weight is.
I think both engines have their advantages/disadvantages.
We can all agree that there is no replacement for displacement. and...before you say anything about a turbocharged 6 making more power than a V8...remember that if you turbocharge the V8 it will make more power still...so, the ease of getting higher hp numbers out of the V8 will be easier than the I6 in the long run...
I personally like the V8 rumble, but, all opinions vary.