Yet despite all these infractions against stated Western ideals, life isn't measurably massively worse in Singapore than in London.

Taboo "worse"!
If by life not being "worse" you mean the annual income or the quality of healthcare or the amount of street crime, maybe it's so. If one values e.g. being able to contribute to a news website without fear of fines or imprisonment (see e.g. Gibson's famous essay where he mentions that releasing information about Singapore's GDP could be punished with death), or not fearing for the life of a friend whom you smoke marijuana with, or being able to think that the government is at least a little bit afraid of you (this not necessarily being real, just a pleasant delusion to entertain, like so many others we can't live without)... in short, if one values the less concrete and material things that speak to our more complex instincts, it's not nearly so one-sided.

That's why I dislike utilitarianism; it says without qualification that a life always weighs the same, whatever psychological climate it is lived in (the differences are obvious as soon as you step off a plane, I think - see Gibson's essay again), and a death always weights the same, whether you're killed randomly by criminals (as in the West) or unjustly and with malice by the government (as in Singapore), et cetera, et cetera... It's, in the end, not very compatible with the things that liberals OR classical conservatives love and hate. Mere safety and prosperity are not the only things a society can strive for.