An assassin wins their fights by dragging them out. Unless their opponent is a total moron and dies to kicks or owaza, say an assassin wins their fights in about 15-20 rounds. This is a very generous estimate, most assassins don't get the luxury of landing ALL their maladicts, they need to pick the ones that will win them the fight and land them before bash does them in, then finish with their trips, throws, kicks, etc. Assassins have very good, reliable, high-damage finishing moves but if they pull these out too soon (or pull out too many maladicts) then they will never get the chance to win the fight. I'm sure you agree with me on this general outline, obviously some assassin fights can be won much quicker depending on how badly your opponent fucks up. With an assassin, your opponent has every chance to choose to flee and the assassin can track them down at their leisure but preferably before the maladicts wear off (mark of the prey + game area knowledge) or assassinate so a fight never happens.
Thugs take this philosophy and turn it on their head entirely. Again, you can change this up depending on your other thief path selections, scrolls, blackjack versus weaponbutt versus ko poison etc. but the basic way a thug thief goes is, load up on damroll, a small bit of HP. Saves and +stat are based on your preferences, but if you have too much of either you can't reach the upper echelons of damage that most assassins don't reach without using their move because a damroll-focused assassin loadout usually gets an assassin outdamaged and killed.
Thugs open with backstab, knife, or trip depending on the situation, and constantly re-engage with knife. They minimize the rounds of actually getting meleed in combat because they CAN'T outmelee the stronger classes. Cheap shot can be used for damage, especially with spike toed boots or if you have a way to exploit a blunt vuln, but it's really used at the end of the fight, when the opponent is going on 40% or less HP, same as parting block. Knife has a sleep multiplier, backstab does not. Pure thugs also have earclap and open-handed separate/grapple to open with (barring malleability, same as a transmuter), which is more reliable than tiger claw and, if added to parting block, becomes signifigantly more dangerous to a mage's health than anything an assassin can pull but a failed assassinate. A thug can also begin his attack sooner, an assassin needs more time to stalk which means more time for a mage to teleport, area spell, word, etc.
Your average thug thief fight shouldn't last longer than 6-9 rounds. If it does, and your opponent is still capable of killing you, you either done fucked up or didn't wear enough damroll or didn't time your attack properly(preps, despoil or lack thereof) or didn't steal enough shit from their inventory. Assassins aren't always better, they're just different. The tradeoff for a thug having far shorter fights than an assassin is fewer versatile options. Any extra tweaks come from other thief paths which denies you earclap or even separate, parting block, or your gear. Assassins have extra versatility but let's face it, short of assassinate and a very situational tiger claw/blindness dust, all their openers are shitty. They also get lame normal poison with everything they do whose only use is an extra -5 strength, a poison effect they (and thug thieves) get from wielding the appropriate weapon.
Thug thieves are also far more dangerous in a group fight simply due to cheap shot and parting block. Those two abilities are the anti-anti-gang code. A thug thief rager is actually equally as dangerous to mages as an assassin with backstab, earclap, knife, parting block and DB.