Being somebody who plays online from a long ways away, I have found OP to be more stable for multiplayer, in so far as I don't drop as much. There are still the occasional D2 problems but it is probably not right to compare the lastest EAW server with 30 or 40 on it, to OP with 10-15 players.
So, with the latest updates making the OP weapons and rules the same as EAW, OP wins on gameplay because it has extra weapons, graphics, and stability.
D2-wise there are now features, like neutral co-op that seems to mostly work which, in my mind, leaves EAW for dead. The only hindrance is that admins are more familiar with using the older, simpler EAW server settings. But, like a petrochemical economy, it can't last. EAW is listed as final, while OP is awaiting at least one more update. Not to say that somebody couldn't do again to EAW, but what's the point? If you are going to spend time adding to a game, then add to OP on the basis of coding lessons learnt from SFC3 which is supposed to be based on the OP code. (OP is supposed to a generation ahead of EAW in code but I have only had this explained to me by outsiders.)
When OP-D2 didn't work there was no question. Now that OP D2 has been demonstrated as no longer suffering from the old problems this is no longer a valid stance.
I'm pretty sure OP uses a later version of DirectPlay too.