One: is it twi or cadence that is the best choice for who wears the metaphorical pants in their relationship from a comedic stand point?
Two which is funnier twi being the sexually experienced/aggressive/kinky and cadence being the inexperienced innocent one or vice versa?

4205733
If you want to stick as close to canon as you can, then Cadance would likely be the pants wearer due to being a bit older and bit more experienced in the whole princess/alicorn thing than Twi. In issues of magic and friendship(and by extension any adventurous sort of situation), Twi would likely take charge.

On a comedy note, having Twilight as the more sexually aggressive/dominant one would be a nice way to turn a couple of fanon tropes on their ears. Even better if Twi still doesn't know what she's doing because she lacks practical experience but she saw it in a book once and now she wants to try it. Cadance being some form of experienced, sexually, but painfully vanilla would make for good laughs too.

4205753 Oh my God I just had the best idea (could apply to any Twi x Princess ship really but for the sake of the group we're in it's TwiDance).

It's pretty late, like past midnight, when there is a knock at the door to Shining Armor's room in Canterlot Castle. He lights his horn preemptively ('cause that's what you do when you're a Guard Captain) and goes to answer it, when it's Twilight. He asks her what's up, and the following exchange occurs:

Twi: You're good with knots, right?
Shiny: Of course, but why?
Twi: Well...I saw a trick in a book involving ropes that I wanted to try with Cadance, y'know, a-and now that we're done I can't undo the knots. And the ropes are too thick to cut.
Shiny: Why can't Cadance use her magic?
Twi: I put a magic suppressor on her horn. And the lock is stuck.
Shiny: ...What kind of knots did you use?

are you proud of me pony-princess-queen/king

4206222 ah shibari rope bondage too bad I can't use it due to shining being indisposed

4205733 I can see Candace wear pant in bedroom, and being a futa mistress at that as well, with twilight as her pet,
outside of bedroom I see twilight wear pant and being in charge cause of her OCD and need for everything to follow her checklist

for sake of comedic I can see it go either way, but mostly twilight want to try something she read in book and it end badly like the two them tied together and they walk to Luna or Celeista door and ask for help,