You can use whatever you want. There were at least 2 quilts at the recent AQS show in Des Moines that had both hand and machine quilting in the same quilt. They didn't look weird at all. As for machine or hand only, that's a personal choice. There are people who swear by hand quilting and others who really like the look of machine quilting. Both are "traditional" methods that were used in the latter half of the 1800's and both can make a beautiful quilt.