Is the Accord a V6 or 4 cylinder? Is it an automatic or manual transmission? Assuming it's a 4-cylinder automatic, it will be rather gutless, but will likely get 5-8 mpg's better than the RL. Gas isn't going to stay cheap so when factoring in mileage, pretend gas is still $4 a gallon. The RL is nice but I have a hard time visioning a 17 year old driving it. It's not exactly an "old persons" car but it's not far off in my opinion. It's comfortable, rather powerful, full size sedan (just like an Oldsmobile or Buick but with reliability).

Drive both and decide which you like more. I lean toward the Accord since it's newer and has lower mileage. But if you test drive the RL and really like it, go for it. Both would make a really nice first car and should treat you well.