Netcode is very important for DOA5. Without solid netcode, the game won't have a decent offline scene. Some games don't need it to have a good tournament scene, but with the current state of DOA's community, I don't see it doing well without solid netcode, even if the game is good.
I doubt I'll have a local scene for DOA5. At most I'll have maybe 10 people and it's unlikely we'll play more than once a week. Without online, I won't have any incentive to play the game outside of that once per week session and therefore I won't want to go to any tournaments since I would have such a small amount of VS. play. I'm good at SC5 because I can spend hours playing every day getting solid practice in addition to our weekly offline sessions.
That said, I don't know any fighting games that have a "good" netcode in which one of the console ports has bad netcode. In MK9, the PS3 version plays significantly better online than the 360 version, but the PS3 version is still terrible. Tekken 6 plays better online on the PS3, but it's still terrible netcode. SC5 and VF5 have great netcode and while some people may say the online is better on one console over another, it's still very, very good on both consoles.
If the DOA5 netcode is good, it won't really make a significant difference which console you play on. But with most 3D fighters, the better competition is on PS3. And for me personally, I don't have enough faith in my 360 lasting to buy it for that system (unless I own it for both consoles).