If you Google "ESEE vs Ontario" you'll find that most people prefer the ESEE knives for their fit, finish, quality control, heat treating and lifetime, no questioins asked warranty.
I have never owned an Ontario knife, but I have 5 ESEEs. They are great, work horse knives that hold an edge well. And if I ever break one, they will replace it, regardless on how I may have misused the knife.
But, for the last 2 or 3 months I have been carrying one of Fatzombie's DAN Knives Mako. Being a custom knife, it cost more than the ESEE 4 that was my EDC, but that hasn't stopped me from abusing it. My knife from Danny seems to hold a better edge and be a more efficient cutter than the ESEE. I don't know if it is the blade design or the fact that it doesn't have that thick coating on the blade that the ESEEs have. The coating does protect the blade but causes more resistance when making a cut through thick material.
If a custom knife is within your budget, don't hesitate to have Fatzombie make you one. Excellent craftsmanship and style.
If a production knife is what you decide on, EM Gear has a small store in Alpharetta, GA and a website at www.emgear.net They stock ESEE knives at reasonable prices.
Here are a couple of pictures of the Mako in some sheaths that I made:
