auto attack:
- simple, less tedious.
- unable to stop attacking while facing enemy unless turning around / move out of range / go to passive mode
(stop attacking to: not give crab type mob tp while its in defensive mode, more hate/enmity control for dps, not wanting to attack mobs with shock spike buff [like gnat] until it's dispelled, in pvp maybe when someone using punishing bard, there are various reason to stop attacking which i'm sure many mmo players understand - and it's much preferable not to turn around or going out of range, especially for a tank)
- however getting haste effect with auto attack will probably help to ensure the full benefit is obtained when fighting head on without movement ( no human / interface lag error )
- fight possibly, maybe, could get more action heavy since pressing "11111" for regular attack is out of the picture, depending how devs go with it - they can create more skills, but it may be tough since most attacking skills are related to tp and skills are limited by action points (though this is probably not the typical final fantasy style... but well there's only one other final fantasy mmo so who am i to judge)
no auto attack:
- repetitive 1 1 1 1 (believe me... my hand is hurting too), i dont really play that many mmo but, except ffxi, mashing buttons are pretty much everywhere whether it's the always the same button or combination of buttons - such as in wow / aion / blade & soul / diablo (more like mouse clicking maybe), keep in mind they are mmo with action bars , not action mmo like phantasy star online / monster hunter. those mmo i played do not require mashing button for regular attack of course, but regardless they are the same mashing button because skills are used repeatedly
- freedom to attack when you wish (please see above for reason to stop attacking a mob), also when you're fighting many mobs that are crowd controlled with ability such as sleep, you can cycle target cursor through the mobs without worrying accidentally attacking the mob (ffxi: "blm casts sleepga II" "thief auto attack, oops!" "blm casts sleepga II" "thief auto attack again, oops!" "blm pulls hate from casting too many sleepga II and dies" "blm - WTF you moron thf!") well, maybe not many people had experienced that, but that surely happened. actually this is not a big deal, but in ffxiv going from active to passive takes a while compared to other mmo, and the players even lose tp in addition when in passive mode.
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anyway... they are just two different systems with both good and bad qualities as many players have previously mentioned.
i think... if they just let you press "1" once, and the action icon lights up and keeps repeating the action at intervals, and press "1" again to turn off the action from repeating - that would probably helps players who dislike full running auto attack, but it is not going to bring the burst damage back from losing the stamina bar system.
p.s. sorry for the grammar / typo, english is not my main language