It makes her look more agile which makes sense with how fast she moves and how high she jumps.
The Other M suit just forgoes all the power and bulk for slim and sleek though.
She's supposed to be one of the most powerful beings in the Metroid universe, the suit looking bulky doesn't mean she can't move fast, the fact that the suit is so bulky normally yet she can still move as fast and jump as high always just made her seem more powerful to me.
I don't ever remember thinking to myself "She shouldn't be able to run that fast or jump that high, her suit is so bulky!" in super, it was never a problem.
And that arm cannon, that fucking awful arm cannon.