I spoke to some gals in a class for their embroidery machines and EACH one has a separate machine for "other" sewing and quilting. They dedicate the embroidery machine to just that. For one thing, once the embroidery runs - it is pretty much on its own until the thread needs changing. SO, are you going to just sit there and watch the machine run? Many of these gals sew and piece while they babysit their embroidery machine.
As for "the best" machine.....that is like asking for "the best" car. It all depends on the features that are important to you.
For quilting, I would put a large throat, needle up/down, needle position shift, good light, motor speed adjust as must haves. I used to think that a built-in walking foot was a must and it is a nice feature to have.
The gals in the class had Brother or Janome machines. Can't remember what models.