Modern engines have the capability to give us both to some extent. Like most, I spend a lot of time puttsing around not wanting to shift too much. But then I hit the city limits and everything changes......give me a lower gear, open exhaust, and lots of revs!!!  When you get close to the braking point and the car is still pulling, it is a wonderful thing.

Those are also published numbers.  If your I6 out torqued your V8 you would never admit it, because what's the incentive for a customer to pay the additional cost of the V8 if the I6 is just as powerful? 

Car companies play those games all the time.  The Corvette is always rated at more power than the Camaro, even though they have the exact same engine.  GM will claim that the Corvette has better breathing and/or exhaust, yet in the real world on a dyno they make exactly the same power.  Its just a marketing ploy.  The top dog has to be the top dog in power too, even if its just 15-20 more HP they get by underrating the Camaro. 

Modern engines are doing some amazing things.  The ability to adjust cam timing allows an engine to have good bottom end AND good top end.  You get into turbos, etc. you can make a small engine very powerful while still having a flat torque curve.  Cylinder deactivation allows V8s to get 25mpg on the highway if you keep your foot out of it, etc.  Saab even had a design years ago that had a variable compression ratio.  Crazy idea, but in the end I think the ability to adjust compression is more easily accomplished by putting a turbo or turbos on a low compression engine and tuning the boost curve accordingly.  An electronically controllable wastegate basically gives you variable compression. 

Consider the first gen Lightning as well.  351 with GT40 heads and intake.  Speed density EFI and a peanut cam (flat tappet for God's sake).  To drive it you thought it was stupid fast even though it had no top end.  A cam swap could pick it up like 75HP, but I would guess it might actually feel slower because you'd lose so much of that seat of the pants off the line grunt by moving the powerband up. 

Its why seat of the pants means nothing.  For years I heard guys say stuff like "I could tell that air filter made a difference because I could feel it.".  When I started racing I found out how bogus all that was.  My fastest runs often felt the slowest.  Why?  Simple, slow is smooth and smooth is fast.  A fast run isn't a tire spinning, getting sideways out of the groove, hairy experience.  A fast run is cutting a great 60' and not missing a shift.  Power's no different.  Torque is what you feel, and where that torque is affects what you perceive as fast.  By moving the torque curve up or down you can make a car feel faster or slower without actually adding or subtracting power, though as you move the curve up due to how HP is calculated you will see an increase in HP, even in a car that may well feel slower.  Bench racing's always fun, but in the end dynos and dragstrips don't lie. 

Its too heavy to.  Those engines have long, heavy con rods, and consequently a lot of weight on the crank to balance it all.  Heavy internals don't spin up fast.  Its as simple as that. 

In part, sure.  The block is also quite heavy because a 300 has a 10" deck height compared to a 302's 8.2" (even a 351 is only 9.2 or 9.5" depending on the year).  The 300 has more main bearings and thus more main webs (7 vs. 5).  In general, the 300 is built for durability and reliability, and heavier parts tend to be more robust and thus both more durable and reliable.  The V8s were used in cars as well as trucks, so weight was always a factor in their design.