That means that the 360 has a faster ethernet card. Something they usually don't put in specs.
The 360 has a better compression ratio I am sure so everything slips through and communicates faster.

It's probably an issue with the PSN servers then. Reminds me of Nintendo WFC the first week that Brawl was out in the USA, there was horrible lag. Last time I played online it wasn't perfect, but it was a big improvement from the first week.

It is getting better everyday, but it will lag on the peak hours. The best time I have found to get on is about 1:30-2:00 pm EST. Thats when it is not too filled up with players, and you can still catch some good fights.