As is pretty well known, in Star Ocean 2 recruiting Ashton comes with a price- you cannot recruit Opera Vectra or consequently her boyfriend, Ernest Raviede. I've tried my best to weigh the pros and cons that I see personally on this page- of course, it's bound to be biased (this is an Ashton shrine, after all!) and it all just reflects my personal opinion- when it comes down to it, it's your own choice to make no matter what. So, with that said, here's some of my reasoning:

Ashton Anchors
PROS
- Single strong fighter, even without KMs (normal attack is very good)
- Potential to be the second strongest fighter in the game (second to Claude) with correct equipment and levelling
- Recruited much earlier on, giving you a better fighting chance throughout the game
- Only character capable of learning Tri-Ace, arguably one of the best [damage and area] KMs in the game
- Recruiting one character (vs. two) gives you more options for who to recruit later on

CONS
- KMs are slow to execute
- Some KMs suffer from lack of range
- Limited to close-range normal fighting

Opera Vectra/Ernest Raviede
PROS
- Opera: Longer range, multi-hit KMs
- Ernest: Normal attack has longer range
- Ernest: You can steal an extra Battle Suit from him after recruiting

CONS
- Opera: Regular attack is terrible, especially for a fighter
- Opera: Normal attack is close-range
- Ernest: KMs lack impressive damage
- Recruiting both leaves one less slot for recruitment later on
- Recruited later on, meaning you go through more of the game with fewer characters
- Recruitment sidequests take much longer than Ashton's sidequest