I'm probably an oddball cause I deliberately installed low-normal XT SGS and low-normal Hone SGS rear derailleurs on my hybrids and mountain bikes. My understanding is that most prople hate them. Don't really need to know why - I'm more interested in what you DO like about a high-normal rear derailleur if that's your preference.
What I personally like about a low-normal rear deraillear myself is that I can leave a stop sign and shift through all the gears while out of the saddle and applying full power to the pedals. Just find the upshifting more positive and controlled in that direction because the cable pull is forcing the shift, not the RD spring.
I do find that whan approaching stop signs when commuting, a high-normal derailleur makes it easier to pull the chain up to a lower gear, again because the cable pull is controlled by the cyclist -not the RD spring. But I like to accelerate myself
You apparently don't have steep hills where a positive downshift is MUCH desired?
No idea. Montreal is an island about 30 miles long, 10 miles across and with a maximum elevation of about 770 feet. There are a few roads that climb Mount Royal, but its more an exercise in hanging in there than in gear shifting. I'll probably upshift a few times after leaving a stop sign, but mostly grind one gear all the way to the top.
But hey - here's what some other people say about it: http://michaelbarry.ca/2010/08/cycling-in-quebec/