After the news of PSO2 on Vita, Sakai received some feedback from the Phantasy Star veterans over his decision to make both versions cross playable. Generally the concerns stem from the handling of Phantasy Star Universe on PS2, how the PS2 version handicapped the updates for the PC version.
When making PSO2 for the Vita, he understood that you all would be wary of such a product, but under careful consideration and examination, they decided PlayStation Vita could indeed handle such a game.
Can PSO2 Vita even handle large-scale updates?
The PlayStation 2 version of PSU couldn't support any large-scale updates at all, they couldn't add any stages nor enemies. But in terms of what they support, PlayStation Vita and PlayStation 2 are two totally different platforms.
For one, there were PlayStation 2's without a hard drive so of course you could not add more stages, or enemies, or even huge system updates. However the Playstation Vita can certainly handle it all.
Wouldn't it be easier to cheat on such a device?
Well in the past, Phantasy Star Online and Phantasy Star Portable 2 stored data offline making it easier to cheat. Even so, they still were able to support the games by banning accounts of cheaters. PSO2 is online only, so data is stored online to keep it secure.
Phantasy Star Online 2 can be played on 3G or Wifi! But the amount of data that's supported on both is considerably different. On Wifi, data speeds were close enough in comparison to PC players. However, for 3G, it will be difficult for the data speeds to catch up, so they have plans to do something separate when you are on that network. (Sakai did not go into detail as to how different the data communication would be on 3G.)
About Cross-Platform playing on Vita and PC
It is possible for the Vita version to play at the same time with the PC version. However, Vita players would have to undergo their own beta testing to see if things go smoothly. It is not what they are aiming for, but depending on the results they may have to say, "PC and Vita players can not play together at the same time."
They received lots of requests on how people wanted to play PSO2 on something other than PC. So they decided to give the PlayStation Vita a shot as a new alternative way to play this game.
March still has some more announcements to go through. By the end of the month, Sakai plans to make announcements about the next test!