I have not played the high-Chaos ending, but I thought the low-Chaos play style and ending were very interesting for this reason: As Corvo you are essentially an unstoppable supernatural murder-machine, and yet you can choose to use restraint all throughout the game. Yes it IS unsatisfying, that is part of the point. Doing the right thing and not being a vengeful killer is hard. Many games botch the good/evil choice by making being "good" easier than being "bad". This is backwards, at least for people who are powerful. Being a complete scumbag in life is actually easier than being a good person, and this basic idea is reflected in the game mechanics. Yes it would be more fun to stab/shoot/explode everyone, and you CAN do that, but doing so is a corrupting experience that will impact the nature of the world (mainly just the ending, but that should be enough).
The story beats seemed deliberately low-impact, to the point that it approaches irony. In the final mission, you are on your way to deal with the people who betrayed you, only to find that Havlock has already killed the others with poison. He stole your thunder. The world ends not with a bang but with a whimper.
Emily, the future sovereign, has Corvo for a role model, and the implied difference between low-chaos and high-chaos is huge.