At Cologne is Brawlin' this weekend we had 3 neutral stages (SV, FD and BF obviously) it worked out pretty well, as far as I can remember there wasn't any problem at all (like "who strikes first" etc.).
Smashville was the first stage most of the time, which is reasonable because it's probably the most balanced stage in history of smash.
However I've voted for Lylat Cruise.
Pokemon Stadium favors stalling through transformations, even if it's only temporary.
Delfino and Siege are out of question in comparison to LC and PS, they might be fine if we look for 7 or 9 neutral stages for stage striking, but not 5, same for Halberd.
They are to influential for many Match-ups.
Edit: I do understand and agree with (Gheb's) arguements for PS1, they're all legit and I think it's actually hard to decide between PS and LC (and YI is controversial anyway) that's why I'd prefer 3 stages.