Good comments, '902'.
One thing that I would mention, though, that I've seen. I wouldn't necessarily agree that "RF is RF".
I've seen some transmitters that just appeared to have better 'range' than others. And I've seen the opposite. Yet, the 'underperforming' transmitters showed just as much power output, deviation level, etc. as the other transmitters. For example, I used to have some GE Master II repeaters (UHF) and they just did not have the transmit range that other brands/models of UHF repeaters, with the same specs, had. I'm seeing the opposite with the XPR-series mobiles. They seem to have better transmit range than other similar-power models (even other Motorola radios), based on feedback from users. I've attributed this to the spectral 'purity' of the transmitted signal, although that's just a 'theory' right now. I've never 'proved it'.
With portables, there can definitely be a big difference between different brands/models, in terms of transmit range. Consistently, I've heard reports from users of ICOM portables that they did not get near as much transmit range as compared to other brands/models of portables (such as Kenwood, Motorola, and Vertex) (and I'm an ICOM dealer, so no one can accuse me of 'talking against the competition <G>). Yet, these ICOM portables will all check out just fine 'on the bench', with full power output and good deviation into a service monitor. The difference here can be the match between the power amplifier and the antenna - in effect, the 'radiation efficienty' of the radio.
I've noticed what you have, that the manufacturers often set the squelch threshold at a pretty high level. I like to see nothing higher than .2 uv, although most receivers will easily provide a 'readable' signal at a slightly lower level than that, maybe as low as .15 uv in some cases, as you indicated. So I tend to take the operating conditions into account (again, as you suggest) in setting the squelch threshold.
John Rayfield, Jr. CETma