[Azathoth]

Increasing your muzzle energy via spring alone is incredibly inefficient. Imagine a inefficient compression system with a M150 spring, and air leaks everywhere. Contrast to a lighter spring M120 which and no air leaks. The increase in efficiency means reduces wear on components and better battery life. More reliability is always a good thing.

As for the tightbore question. It depends on the bore in question. Just because the inner diameter is smaller doesnt make it a more accurate barrel. Straightness, smoothness of finish, inner play a role.

For years and years the thought has been that tightbore prevent BB's from rattling along the inner edges of a stock barrel which at the time was between 6.08-6.12mm. Nowadays bore are coming stock 6.04-6.06 which has been the traditional tightbore range. For YEARS moving from stock barrels to tightbores have been advantageous and was supported by the player base. However, the tighter the bore the more likely that debris/dust will cause fouling, and after "X" rounds you will need to clean your bore or it will not be performing as it should be.

About 3 years back a bunch of people Japan/phillipines theorized that it's not the bore diameter that mattered but the relationship between BB diameter and the bore. Hence the early widebores came about. You can read on their websites regarding the theory but in a wide bore debris is not as big a factor.

TL;DR
Stock to Tightbore = generally higher FPS, better groupings than stock
Stock to Widebore = Generally lower FPS, better groupings than stock.
Tight to wide = lower fps, Typically better range 15-20ft, wider groupings from my limited experience.

Tested on PTW, i can hit a dinner plate sized group at ~250ft with the PDI tightbore. With the widebore I can hit a 6-8ft sized grouping at 270. at 250ft I get a 4ft sized group, With stock systema barrel 2011, I can hit a man sized group at 250ft