Just plan on losing alot of sleep : ) because you'll spend alot of quality time with this game.
Phantasy Star Universe is more well organized and thought out. First of all they changed the way you equip weapons so that you don't have to waist time looking for a specific one. They made it so you'll have them at your fingertips and the same thing goes for select items. Don't worry they'll teach you when you first start and its not hard at all. PSU's story is really good and a major improvement on the previous games. The way it's told is through movie cutscenes, messages, talking to people and animated in game scenes and its real easy to follow if can read above the 3rd grade level and are patient enough to watch, but in all the story connects very well. There's also three planets to explore filled with enemies to defeat, items to find and bosses to run from lol. There are a variety of weapons along with a number of ways to power them up. First you can equip you weapon with a TECHNIC and it will level up the more you use it. Second you can synthesis your own weapons and armor from items and elements you find in battle. These can then be upgraded at the shop specifically for upgrades. Graphics are an overall major improvement in the least. Three planets completely diverse from each other in stunning detail. Bushes, trees, rock clouds, water, lighting, even the background looks nice. The clothes on the characters are even detail nicely. Well graphics are better seen instead of read about so i'm going to move on.
Boss battles are fun and takes more thinking instead of just hacking away. Bosses actually defend themselves this time around instead of staying immobile and attacking you. They'll back up, block, move out of the way, retreat if they feel they're getting hit too much. They'll go recover then they'll come right back at you full force. Finding Items is more rare in this game especially weapons. You'll mostly find stuff you can't use directly but need for synthesising. This way you have more control over creating the weapons, armor, items that you want instead of it being random. Same thing for rare items.
There's alot more good things to be said about this game but for every game there's always atleast one drawback. For PSU i'm sorry to say there's no Offline Multiplayer. It's the only thing missing and yea it was a big feature but maybe it was left out to motivate more people to play Online. Other than that this game is definitely worth keeping and spending all the hours of the day and night on. Don't forget to eat tho. . . . . .