Asiana Airlines vs. LCCs: Is Asiana definitely better?

I am traveling to Osaka.
A round trip on Asiana is 289,600 KRW per person,
but the price difference with LCCs is only about
50,000 KRW per person, so I am debating.
Is Asiana using the Airbus A300? The plane looked quite large.
The seats will be a bit more spacious, right?