See baby is already 6 months now and its time when baby start sitting and soon crawling. Bbay will crwl and explore things around and high chances of jumping or getting out of the bed. So, crib is better option among two. because its has high railings and many brand offers adjustment with the railings also. But cribs are expensive and bed railings are cheaper as compared. You can check baby shops. I have seen good in chicco brand.