What is the "BEST" engine, oil, radio, plane, pie (uumm pie), prop, servo, etc. It doesn't exist because it's all opinion and there will never be total agreement as to what is the best anything.
Pat Roy, known as Tired Old Man on most of the RC forums, makes his living working with gas engines. He is about as knowledgeable on 2 stroke engines as anyone alive. He stated on another forum that a reasonably maintained engine should last from 300 to 500 hours of operation. He did not specify a particular brand of engine so I would have to assume his statement applies to all brands. The key is being maintained in a reasonable manner. I'm sure that would include using a proper oil ratio to gas, proper air ventilation, needles set so the engine doesn't run too lean or rich, prop that lets the engine run in it's designed range, etc.
Now, I currently have 7 gas engine planes. I only fly one day out of a week and have only room to take one plane to the field each time. I try to rotate them so each one gets to the field about once every 7 weeks. Then on that day, the plane gets flown about 3 times at about 10 minutes per flight or in other words about a 30 minute run on the engine each session.
I think it is safe to say I'll never wear any of my engines out within my lifetime. It's far more likely I'll destroy an engine in a crash than ever wearing one out.
Therefore, for my circumstances I find the less expensive engines (DLE, VVRC, etc.) to a better value than the high end engines (DA,3W, etc).
So when you ask what is the "best" engine, you should consider many more factors than brand name alone.
Mike