Just two points I want to focus on most:
They're not exactly the same, though, especially so long as you return timers to Disciplined Fist and Demolish, though there may, yes, be a best choice in each GCD.
Skills with high individual damage are best used under damage buffs. Everything else is best used under speed to increase the portion of uptime spent on stronger skills, because amping the weaker skills by 5% is not worth as much as getting through them 5.3% (actually quantized by durations, but this is just a spherical cow) faster and thereby increasing the portion of stronger skills that are then further amplified.
Like, if we want the stances to be choices at all, then we're going need to have...
- branching paths that still ultimately (though in complicated fashion) have a best answer or
- clear best answers across a 60- or 120-second period (due to Blitz, Disciplined, and Demolish line-ups), or
- at minimum, preferred stances for each action (Wind for low-pppgcd [personal potency per gcd] skills, Fire for high potency-GCDs where oGCDs in gap are obviously included),
or...
- as before, Wind and Earth are dps losses used only as a last resort and rarely able to make any real difference to survivability or mobility anyways (unless you amp the hell out of them, risking making Earth OP overall, or redesign them to use a sort of granular resource)...
- at which point, you might as well have Wind and Earth consume MP and remove Fire altogether, or
- turn Fists of Fire into your granular Riddle of Fire phase -- perhaps only affecting beast skills or adding flat potency if worried about them being overly obligatory for oGCDs and/or Blitz or applying some other way to force stance-rotation, such as, idk, ramping drain costs from staying in a given stance too long.
Whatever the case, adding that allows for some small-gap skill-expression akin to Shadowbringers positionals for those who like a stick-shift feel that's less hamfisted and not nearly so wasteful as Shadowbringers' stances.