Fighter vs Thief

There have been some comments about how a single fighter is probably better than most parties and a single thief is abysmal. I don't dispute either of those claims. My question is, at this point in the game (gearing up to fight Astos) just how comparable are the two classes? I haven't gone over the defensive numbers yet, but offensively the differences are:

• Fighters can use the silver sword, thieves can use the sabre. The silver sword has 10 more damage, 10 more hit, and 5 less crit. Unless you're playing on the NES that is, in which case it has 5 more crit than the sabre.
• Fighters get 3 hit per level. Thieves get 2.
• Fighters are guaranteed a strength gain every level. Thieves don't, but I'm resetting every time I gain a level that doesn't include a strength so I actually keep pace here.
• Fighters start with 15 more base strength.
• Fighters start with 5 more base hit.

Assuming Tuesday's post was right I need 3 hits to win as a thief. (Turns out I actually won at level 25.) This requires level 28 to accomplish. A fighter, on the other hand, gets his 3rd hit at level 14. The thief has a base damage of 29 at level 28. A fighter has a base damage of 33 at level 1! He may or may not live as long at level 14 as a thief does at level 28 but if he does he deals way more damage. At level 14 he'll kill Astos in 11 swings on the PS and in 9 on the NES compared to 26 and 23 for the thief. Ok, so we need to delevel the fighter even more so he only gets 2 swings per round. Even if we knock him down to level 7 he still wins on both the PS and the NES in at least 1 fewer round on average. On the NES he actually doesn't even get worse than the thief until we take away his second attack. That's right, a level 4 fighter with 2 swings per round is better at dealing damage to Astos than a level 28 thief with 3 swings per round is. But he'll have a hard time living through 7 rounds... Or will he?