For a really nice vintage top that has been hand pieced, I would look for a good handquilter and pay to have it handquilted. (You do have to check on the quality of the quilting before hiring someone; have heard horror stories of "hand quilters" who used doubled thread, made large stitches, and did not know enough to hide the knots.) From what I can see of the grandmother's flower garden top, it would fall into this category for me.
Vintage tops that are not all that nice and/or that have been machine pieced, I would definitely machine quilt myself.
I think you have to make the decision on a top-by-top basis.