As noted meter sensitivity varies from stb to stb.
Signal strength is a measure of the how you are powering you lnb so is very specific to your set up. Across a range of brands and set ups for working Ku systems S values seem to be in the 70 to 90 range. As long as its consistent, higher or lower may not make much difference in this range for any stb/lnb. If it gets too low you may not power the lnb properly and may not get the signal to the stb.
Quality is a measure of the signal being received from the sat and is a function of the quality of your gear, how well you aim and how strong the particular tp is (you can look at signal maps to see footprints). On the same sat different TP's may vary in Q reading and you can tweak you dish to make some TP's on a sat to come in better than others on the same sat. Higher Q is always better and for Ku you might have a a swing of 10% due to changing atmospherics (say clear sky to rain). The key is do you have enough Q to watch tv without pixelation. Again for Ku, Q values for watchable tp's seem to be in the range of 25 to 90 across a range of stb brands.
On my S10 in the Toronto area the best I get with a 90 cm fortec type dish is about 75% Q on any sat from 61w to 125w but can watch tv at as low as 5 - 20% (S is about 85). Hitting the same sats with my old VS Ultra, it maxed at about 72% and s of 78%. On 101w in a clear sky, I get Pentagon HD at 75% and on 97 I get RT and Al Jazzera at about 74% on my S10. I might be able to get them in better but with having a motor I have tweaked the dish aming to make 125w better and 61w slightly less than optimal. Regardless of your set up and aiming you may have lower Q values in Montreal if you are in a weaker signal area for many sats, you can't overcome this.
For me the meters are the tool to be used to opitimize aim and after that its simply can I watch a channel or not. With a well set up dish, the S and Q you get are what you get.
