The reason I like reducing tick sizes (and I mean dramatically like 1/1000th or more) is less about the bid ask spread at the middle, but rather the competition at the +1 levels. A lot of the latency advantage right now is in being able to cancel a few levels near the midpoint while leaving tons of other orders stacked.
Reducing tick sizes would make these deep stacking strategies less viable, which seems (though I have no proof) like it would make the positions of the market makers less risky in a systematic way.
As for GOOG vs MSFT, I think that is obviously explained by the much higher price of GOOG right? Nothing is going to make holding a stock that costs more less risky, even speed.