Avon and Stringer obviously worked better together as a team, when they had a "crisis of leadership", things fell apart. Stringer had the right idea in terms of wanting to go legit and not beefing over street corners. Avon even said "Stringer was right...fukk this war, all over a couple of corners". But Stringer went too far in his ambitions. It took Levy a few seconds to figure out that Clay Davis played him, then proceeded to laugh smugly in Stringer's face.
Stringer had the "smartest man in the room" complex, just look at how proud he is of himself because he learned the term "market saturation".
Taking a couple of business courses at a Juco doesn't exactly mean you can apply those same principles to selling heroin and cocaine.
Avon had smarter instincts. He was able to read right away that prison had changed Cutty. The little exchange at 0:45 says so much, and later comes into play when Avon isn't mad or surprised when Cutty tells him he wants out.
Avon knew Stringer screwed up on the Orlando hit, he knew Marlo wasn't someone you could really reason with.
So overall I thought Avon was smarter, but was on a serious power trip in season 3. I like Stringer's mentality of having money and freedom over having the power and having "your name ring on some street corner", but he obviously fukked up too with all his duplicity, and the worst of all was getting caught on the wire talking about planning a murder of a STATE SENATOR.
For Stringer, that's going backwards like 100 steps.
In the end, Marlo has what Stringer wanted with all those business opportunities. But Marlo doesn't want it, he wanted what Omar had, even in death. Those guys on the corner didn't know who Marlo was, but they were talking about Omar.