Well I can say that infi answers all your requirements and has the toughness.
It's really easy to sharpen; most of the time it just needs stopping, or steeling if you've managed to roll the edge. It doesn't need steel removing to sharpen it most of the time like some other steels.
It's known for not chipping; it will roll or (with more abuse) deform (dent) instead. I've had a small dent in one and it almost completely realigned by steeling.
Edge holding is great. I've battoned hardwood, 4-5" thick logs into quarters and smaller, probably about 12-16 feet of them with my Heavy Heart and it's still shaved arm hair. Stropping for a minute made it hair popping again.
Infi has the best balance of properties, in my opinion. For the ultimate in infi edge holding, the Bony Active Duty has a harder heat treat and they are still available.
Edit: Perhaps I should add that I also have O1, A2, CPM-3V (Fehrman) and assorted stainless. Infi wins every time for me. That's not to say some cant get close, or even exceed infi in some attributes, but none give the wide range of high-end attributes that infi does.
Getting just the right knife might be more of an issue than the steel though; there are a lot of excellent knives made from other steels than infi, which comes in only a few shapes at around 4". At 4", plenty of folks find other steels quite good enough; even Busse fans!
