depends on the use case, sitting at a desk i would take $500 headphones over iems for the comfort over long periods and sound stage every time, but i have a $300 pair of iems that i use almost every day at work where I'm always on my feet and every night in bed where headphones would fall off or get crushed. I love them both, but they each have their niche. If you have neither, I would split and get one of each for $250. hell, good iems are getting cheap so $150 on iems and $350 on headphones gets you into high quality stuff on both sides. I'd just browse r/AVexchange until something catches your eye lol

just sayin rn you can get HD6XX + LetShuoer S12 + Fiio BTR5 for about $450 total and be happy on all fronts