there's no right or wrong answer for this. it depends on what would suit YOUR family best, or if you're renovating in preparation for a sale, what your realtor suggests would make your home more marketable according to the stats in your area.
my laundry is downstairs. it doesn't faze me one bit. i like it down there because there's plenty of room and i don't want to sacrifice the space in our upstairs (we have a rancher), and going up and down stairs doesn't bother me. maybe when i'm older it will.
so for US, keeping your downstairs bedroom intact would make more sense, especially since we've cannibalized our 4-bed home into a 2-bed one, so don't have as much guest space as we'd like.
but we're not you.
does your downstairs bath have a shower? if not, that's something to do for sure.
so the only thing you need to figure out is if you need more guest accommodations, or if having the laundry upstairs would significantly improve your regular round of chores.
khairete
S.