I would vote for "it depends" train of thought. 99% of the time I construct the quilt in smaller sections rather than one whole unit. I plan then go ahead with the assembly of the quilt. I do this for any size of quilt, but it seems to work for the largest bed quilts the best.
If I had a choice, I would go for the largest throat space that fits my sewing area. And keep my other machines for what they seem to do the best. Not an ideal world, but what is?