efix
RF user by conviction
Personally, I like the sonnar look and the shift has never been a problem. But, since you are using an M8 with a crop factor the 50mm f1.5 Sonnar would be approx. 75mm. I think that is the issue for the M8.
The M8's crop factor is not the issue, I've gotten used to the different field-of-view and use my lenses accordingly. But I've had the 35/1.4 Nokton which shifted quite heavily, and I didn't at all get along with it. Also, the Planar is more affordable for me 🙂