the numbers 21 and 22 tell us nothing about the bikes actually fit
although those frame sizes
when applied to mountain bikes or hybrids
tend to be large or extra large
and you potentially could ride either one comfortably
but every bike maker is different
s there is no direct comparison that can be made just by knowing
one is 21 and the other is 22

so my advice is
neither

find yourself a used road bike
in the 58 to 60 cm size
or whatever size you can adjust the seat to get proper leg extension
and have the post in past the minimum insertion mark
and still be comfortable riding the bike

for 400 dollars you might be able to find something quite nice in the used market