Have had both. The older Kokens with knurled handles are amazing if you can live with the lower 24t. Hazets are smooth, but higher backdrag. Question can only be answered with what you value: local support & price vs backdrag & slimness
Just got done lubing and finger-banging the new 3725ZB 3/8" quick release. Initially ordered the 2725ZB (3/8 dr in 1/4 body), but instantly regretted it; felt it was too damn small. Also used a MotivX oil filter wrench to mess around.