I can't comment on the Quick Load G-III 17. The Olympus 35 SP, is a battle axe, but its my battle axe. It' a big camera. The shuter speed ring is rather knotchy versus smooth and the meter is housed outside of the filter ring, (manual filter compensation required). Also, the shutter is a bit noisy, as its mainly in the lens barrel. That's the bad news.
The good news- there isn't the usual switching back and forth to the "A" mode, when shooting manually. The meter is always active. The meter reads in EV numbers, which I'm used to. Hence it doesn't peg into the over or under exposed red zones like other viewfinder meters. The meter matches and exceeds the acuracy of my Gossen hand-held when used as a reflective meter. There is spot metering capability too.
More on the plus side. Larger than average, bright viewfinder, but alas no parallax compensation for the frame lines. Manual shutter speeds range downward to 1 sec versus its competitors 1/4 second of 1/8 th sec. The camera uses easy to find 49mm filters. The seven element Zuikolens is superb and will match the best in class Konica S-3 Hexanon. With regards to the lens, it is at times too sharp. Color rendition / micro contrast deliver photos that seem more 3D than others I've used.
With regard to the auto mode, I never use it, but it works in daylight. In low light it will lock the shutter release to prevent you from underexposing the neg.
Now here is what I know about the Canonet,. It certainly is prettier. The gizmo for the quick load feature is centuries beyond anything I'm used to. Ergonomics have to be better than the 35SP, but what do I care.
Take all of the above with a grain of salt as now a days I use a 1956 Kodak Retina IIIc more than I use the Oly 35SP and the Retina isn't a camera for the ergonomically challenged.