It depends on your machine, but for me I find that my vintage sewing machine does very, very well with human sized garments but teeny tiny seam allowances for doll clothing more often than not get eaten up by it. Though I've found that simply increasing the size of the seam allowance and cutting away excess fabric before ironing it does help, it can lead to wasting a lot of fabric. Hand sewing doesn't have to be done for everything though I've found that depending on your machine, it's just more practical in the end to do it all by hand, even if the machine saves time it's just much easier that way.