The electrification of KW is interesting. I think all along people who follow this stuff believe the future (when money is available) for GO is to electrify all the lines and, I believe, there had been general consensus that the order should be 1) Lakeshore East or West 2) Lakeshore - whichever did not happen first 3) Milton or KW 4) Milton or KW whichever did not happen at #3 ...then the others. The actions of the the CTC seem to have forced the hand and made them announce the KW electrification first (although I think that is more of a PR move than anything and won't happen in that order).
Comparing the size of population around lines can lead to a silly discussion sometimes and things like re-combining the Lakeshore E and W lines to "win" the battle. If we "re-split" and focus on, say, Lakeshore West......
The municipalities that are uniquely served by this line are Oakville Burlington and Hamilton......combined 2011 census populations of 878,248. Using my favourite line (KW) the uniquely served municipalities (Brampton, Georgetown, Guelph, K-W) have combined populations of 1,003,682.
Then you are left debating/wondering what parts of the populations of Toronto and Mississauga to include in each's "catchment" area. That sort of difficulty is why the people who get paid to plan these things rely more often on density (combined population/residential and commercial I think) than raw population numbers and I believe one of Metrolinx' own reports identified the then GTown line as the transit corridor with the second highest density in the region (2nd to the B-D subway I believe).
It is all difficult to figure out but I doubt you end up at a conclusion to support one line "deserving" only rush hour one way service 5 days a week while the other's population warrants 7 day a week two way 30 minute service which is further augmented at rush hours.
There may be other reasons to have that disparity of service that are not clear to me but your statement that it is warranted because "there are simply more people along that line" is not likely supportable.