I'm not familiar with the merits (or otherwise) of a 455 vs a 377, but I pass on 222s (Meridians) and wait for HSTs on the MML when I can - mind you these days I know the timetable well enough to only turn up for HSTs (and occasionally get a nasty surprise when a 222 shows up!)
Andy
Basically, you might not want to get a 455 because on balance the 377 normally has better seating in parts, generally better HVAC (debatable, admittedly), a marginally better ride depending on preference, and a nicer interior ambience (in my opinion). I too don't get 455s by preference but that's for a different reason - I recently cut a large part of one of my fingers, very nearly severing it, in a 455's door, so I have quite bad memories of them!
I'm not overly fussed about Voyagers, although I will always aim for a HST. If I know a TOC is operating similar classes of train but one is a bit more comfortable, I will do my utmost to time my journey to get the maximum comfort (e.g. I will always try to get a 166 over a 165).
Some train classes are too unreliable for them to be a sensible option. I will avoid 442s like the plague if I can use a 460 (supposedly soon to be a 458/5 and no longer on the Southern network at all
despite their much-needed reliability) or a 377.
As for "snobbery" on other fronts, I am a bit of a "TOC snob" - I will avoid FCC if I have a reasonable alternative. I also avoid the inner reaches of the Central Line on the Tube because I find it is unnecessarily crowded and uncomfortable for many journeys I make.