Before talking about the differences between Second Story and Second Evolution, let's talk about the game in general. For those of you who have played The Second Story and want to see the differences that were made in Second Evolution, scroll down to where Welch and the YouTube video of the game's trailer are at for the details.
The Star Ocean series is known for several things among RPG fans; the action RPG combats, the Item Creation mechanic, good replay value for having multiple, different characters to recruit in your permanent party, Private Actions and how it affects the multiple endings the game has to offer as well. These are features that made the Star Ocean series popular when they were first released. Being that Second Story was the first Star Ocean game that was released in the US, it is considered to be a classic among many RPG fans.
Outside of combat, there is the Item Creation system where you use your item creating skills to turn ingredient items into more useful items. There are many types of Item Creations which require different skills in order to learn, like Crafting, Cooking, Black Smithing, etc. Utilizing these Item Creations can be of great help on the journey by getting you better equipments early, having more potent healing items, and/or even items that may teach your characters skills and sometimes even special moves used in combat. Then there's the Private Action system, where you and your party can split up and go act on their own in cities and towns. This gives you the opportunity to talk to your party members in town, sometimes triggering an event that can affect the characters' relationship with each other, or have other effects.
The graphics of the game is fairly unchanged from the PSX original; using the same sprites for the characters and monsters, mostly same map images, and the existing cut scenes from the original remains unchanged. So graphically, it might be a bit dated, but this is a port rather than a remake. What changes that have been made are in the character portraits, which has undergone a redesign in Second Evolution. The redesign is slightly more modernized in art style in comparison to the original character arts from Second Story. You will see the characters' faces, often with the appropriate facial expressions (with the exception of Ernest... for some reason), during their dialogue.
The sound department is mostly the same as well, in that most sounds and music are left untouched. Of course, one of the biggest change you would notice in this game is the new voice acting. Most of the dialogues in the story, and even some Private Actions have been given voice acting, which is a neat addition to the game. As much as I'd like to comment on the improvements on the voice acting from Second Story however, it's hard to say as I've played Second Story in Japanese, while having played Second Evolution in English. It was definitely a big difference for me, combined with the new character art as well, but they both eventually grew on me.
Replay value is naturally high because of the variety you can have in each play through of the game. The maximum number of characters you can have in your party is 8, but there are 13 playable characters in Second Evolution. That means, you will not be able to recruit 5 of them in the same game, and will also mean that you should consider what character combinations you want to have at the end of the game. On top of that, you also choose who your main character is between Claude and Rena at the beginning of the game, which will change the perspective of the events you view from that of the main character. Finally, the many different possible ending combinations you can have will make each play through rewarding with a different ending for your characters.
To add to replay value, there are also harder difficulty settings you can choose at the start of each game to give yourself a greater challenge as you learn the tricks in the game. Utilizing Item Creation well can allow you to dominate the game with ease on the easier difficulties. So this gives the option for those who want a cakewalk with the game to be able to breeze through, while those seeking a challenge can unlock the opportunity to do so if they choose to do so.
Finally, the changes made from Second Story. Above, we have already covered that Second Evolution has new character art, new voice acting, and a 13th character that was never in Second Story. That 13th character is Welch Vineyard. Her first debut being in Star Ocean: Till the End of Time on the PS2, she makes an appearance in Star Ocean: First Departure and Second Evolution as well. She is a melee fighter who uses her poking stick as her weapon, and can flick, slap, and punch enemies senseless.
Other big changes made in Second Evolution is that all melee fighters can do a 3 hit combo with their normal attacks. This definitely makes damage dealing faster, although after the third chained attack is a long recovery time before you can make your next action, unless you cancel the recovery time with a special move, much like how you would in a fighting game. Another change that affects combat is how Spell Combinations was removed. I'm not entirely sure if this change was really necessary, or beneficial in any way, but I was slightly disappointed by this. I actually liked the Spell Combination system in Second Story. ._.
Then there are minor changes, like changing the name of items, skills, and changing the censored character names back to their original names in the US. There may be a bit more subtle changes that were made, like higher resolution graphics, and widescreen view, and such, but this is getting into the very technical, minor details that a normal gamer wouldn't care too much about, at least as far as what matters for the selling point of the game.
Of course, the biggest improvement IMO is that they fixed the game freezing on a black screen after combats in Second Story. This happened so frequently for me on Second Story that I never really finished the game until now on Second Evolution. However, I DID have an issue with the PSP freezing on me when I got a Game Over screen, which required me to pull the batteries out to even turn off the system. This can be easily avoided by leaving the game when your party gets wiped out via the PS button. Considering that you're forced to load back from your saved game when you get a game over anyway, you won't be losing out on too much when it happens anyway; just a minor hassle if anything.