This is just my personal opinion but I think that the Keen Kutter K series planes are the best bang for the buck when it comes to metal planes. I am restoring a Keen Kutter K5 for myself. The blade needs a little help and I am considering an after market blade I use an ECE smoothing plane and it has an A2 blade I believe. As a Tool and Die Maker mostly dies I have a lot of experience with A2 and I am not a big fan of O1. It has limited usage in die making. The cutting edge doesn't hold up.
Anyway I am considering an aftermarket blade of either A2 or PMV-11. I hear that the PMV-11 edge holds up better than A2 but isn't any more time consuming than A2 when sharpening..
I would like too hear from those who have experience with either blade types, both the pros and cons. and why you chose what you did choose.
I would like to thank you in advance for your answers and your time writing them