Hand or machine quilting? What does the backing look like? Do you like simple or elaborate?
I am not trying to be rude by answering a question with a question. How elaborate will your skills allow you to be & how long do you want to spend quilting it? If you are using a busy backing fabric, then most of the quilting will not be easily seen if sewn by hand or machine, so it comes down to your preferred resulting look. Do you have a more simple backing that might could use some "dressing up" with a bit of extra quilting? In the ditch will make a nice geometric pattern on the back. (If you do this by machine, I highly recommend a walking foot.) You could ditch quilt around the squares, & outline the flower motifs by hand or machine. The choices are endless!! :D