You are still missing the point. Not a big deal. Just don't want you to think I am blowing smoke. There are a LOT of slow big blocks out there and plenty of slow small blocks as well. If both engine are built to the hilt and are making maximum HP then you are right the larger engine has the advantage. The truth of the matter is, most of the cars on the street are not "maxed" out. Most of the cars at the track fit that description too (on average Joe night). This is the difference. You are asuming an optimized 400 against an average 377 in that case you are right. You said yourself max rpm or 5500, I'll give you your 400 with 5500RPM max and take a 327 that has no rpm "limit" attached and blow the doors off the 400. I used that as an example to make my point. Once again it's all about combination, it's that simple. If you build the car to make the most of the 400 and it's torque it will be a heck of a car, the same can be said for a 377 with it's rpm and HP. With the few details that were provided there is just no way you can say which engine is best for his situation. There are very few substitutes to cubic inches but there are a few.
By saying the 400 is only good to 5500rpm you are saying, it is a very mild build (far from maxed out). With that said a slightly more "maxed" out smaller engine will be just as good if not better.
Once again I am not pushing the 377 and I personally see few applications that I would build one for (one being a stick car with steep gears, pro touring type car).
If you have the choice between a 350 and a 377 build the 377, it will make more power and RPM better than the 350, it's a win win situation. I would take a 383 or 400 over a 350 any day of the week, for all different applications.