Oh, the Pirate is definitely a much better fighter than a Thief. At very low levels the Thief may have an advantage but the leaf turns at higher levels. The Pirate has:
* Better Dodge (as you already said) which often doesn't help much against regular primary attacks but can make a difference against iterative attacks and Power Attacks
* Two-Weapon Combat for free, i.e. one extra feat,
* Uncanny Dodge -> not especially vulnerable at beginning of combat
* Improved Uncanny Dodge -> cannot get flanked, und thus can move about the battlefield much more freely
* Mobility chain -> first gets resistant to AoOs, then immune, then can perform a Move and Full Attack action in the same round
So in short, a Pirate may not get as much Sneak Attack as a Thief per hit, but he is much more mobile and eventually gets up to 6 times as many attacks as a Thief:
where the Thief moves in on a vulnerable enemy, or feints to be able to Sneak (note that he can't move, feint and attack on the same turn), and may succeed to kill a single opponent with the one blow he has...
...the Pirate can perform up to 3 main hand and 3 off hand attacks, moving between any and all of these attacks up to his movement rate, and especially in the first round of combat kill up to 6 opponents at once.
Also, if the Thief's fails to kill his target, he may try to move out and will draw an AoO, but if he holds his ground the enemy may Full Attack the Thief on his action, which will be very unwholesome for the Thief...
...whereas the Pirate just needs to keep 10' of movement in reserve, and after doing his attack(s) he simply jumps back ten feet without drawing any AoO, and any opponents going after him will only get a single attack each.
In other words, if the Thief tries to survive the rest of the round after his damage output, he will be very limited. A Level 15 Thief may do 1d10+8d8+Str in one blow, but having to pick his targets carefully means he'll also _get_ only this one blow. Note that he has to end up with not 5' but 10' of free space between him and the next active enemy if he doesn't want to get hammered by a Full Attack.
Whereas the Pirate gets up to 6 attacks at +5d6 Sneak attack (which will usually suffice to trigger MDS), so potentially up to +30d6 just in sneak attack per turn.
Of course the Pirate will only be able to Sneak multiple opponents on the first round. But that first round means he can very reliably kill up to six enemies, where the Thief will score only one, except if he uses a bow, which increases his potential to 3 or 4 kills, and that's it (and he'll have to switch weapons after round 1).
...and he says the Pirate isn't a more capable fighter than a Thief! :lol: (no offense meant but I hope I was able to enlighten you)