Less than going too large. Too big is just that. Not much you can do. Too small? Can be dealt with. I'm riding 6cm too small on one bike. 52cm when 58 cm would be ideal. Took some modding but iti can be done. Take though a less
extreme example. I need 58, I have 56. No problem, taller seatpost, longer stem. I have a 60 and need a 58? Itws just goiing to feel wrong. You can shorten the stem, but can't do much about the seatpost.

Going small you might get shoe overlap on the front wheel just adjust technique.