Phantasy Star Portable 2 is a pretty noticeable improvement over the previous game. For instance, enemies and AI companions are no long feel like mindless zombies. The former is far more aggressive and puts up a decent fight, while the latter no longer stick too close to you and use spells when they're necessary. Combat received a massive upgrade, adding an ability to block and dodge, lock-on that actually works, secondary charge attacks, armor swapping, better disc types, and a superior upgrading system. What bogs down the experience are bosses, thanks to their questionable hitboxes, massive health pools, and counterintuitive aiming (which locks you in place). There's a traversable hub now as well, which while appreciated, takes away from the experience of traveling to other planets. The story is completely uninteresting yet again, revolving around an ancient civilization returning to possess their creation.

Infinity adds a new race to play (Duman), more weapons, infinity rank missions, rebirthing (think Disgaea), custom missions, and alternative charge shots, making it the definitive experience.

PSP2i does a remarkable job of bringing Phantasy Star's grindy, dungeon-crawler gameplay to a handheld. This is probably the most refined game in the Universe/Portable series: the combat system is more engaging than previous iterations, balance changes make more weapons/playstyles viable, and there is a ton of content to explore. That said, I'm not motivated to dedicate time to this game right now. The story isn't compelling, I'm not that into RPGs, and it lacks the nostalgia factor of the original PSO for me.

This is definitely worth a shot if you have a handheld and are into action RPGs; make sure you set up the English translation patch. If you only have a PC or console, maybe look at PSO2 instead.