PS2 update of GBA games improves visuals, VA, extras. Some good new systems with the ability to form squads with two units, allowing up to four units to attack together if nearby allies have the support ability, squads allowing access to a new pilot skill for each character. Weapons capable of double attacks that can hit a unit or squad and an adjacent target. Also includes a 2.5 game with another 12 scenarios to set up the next game.

The first game hasn't aged as well and outside of a portable GBA format just isn't that impressive. Way too easy, dull enemies for much of the game, focus on original characters lead to very limited units, weapons, characters, and music making it a much more mediocre entry in the wider series.

The sequel is an improvement on the first with a much more varied group of enemies, units, weapons, character options, and a better plot with the story having a few path splits where you choose what group to be with instead of having a non canon route that would have you playing through simple missions on a second playthrough. Some odd choices when it comes to hiding unique units behind completing hidden tasks, some unfitting ace bonuses, and there are more unique units but many units are copies of others.
Screenshots
OG1: https://twitter.com/Legolas_Katarn/status/1424181699118735365?s=20
OG 2 https://twitter.com/Legolas_Katarn/status/1437191963514572801?s=20