Although this thread is old, the difference remains the same. Simply said, "The People" make the difference.
I found no evidence of Inworld residents openly dissing SL nor do I find the opposite SL residents dissing Open Sims. There are those who cut their teeth in SL and will not leave until the power goes off at Linden Labs, while others have the very same pioneer spirit to explore other worlds, that same spirit which created Second Life. There is good in both worlds, shortfalls as well.
I am a resident and creator in several worlds. Looking at the numbers only, growth is extraordinarily fast for the Open Sim grids as opposed to Second Life which now matures slowly, Open Sims are bustling to improve and successfully gaining market. Is there anything for Linden Labs to fear? I seriously doubt it. Why? Because as a creator in several worlds, I am not alone. There are now three major market places and three major currencies that convert to cash.
Second Life can afford to shrink by 5% per year for the next two years and still lead the other two markets. However, like IBM and HP quickly learned, they cannot rest on their success forever.