I think the dead bar depends a lot on personal preference in combination with how many quilts you do. I do not have a dead bar on my Voyager/Hinty setup and do not miss it. I did install Bower lifts so it is easy for me to adjust takeup bar height when I need to, which is not for every roll. However, I do not quilt for long periods of time. I quilt just 2 or 3 hours per day when I have a quilt in the frame, which is not every week, and quilt only for myself. If you quilt for others or do a lot of quilting every day, a dead bar eliminates the step of adjusting height when rolling a quilt.
The type of batting you use can affect whether or not you can roll a king size quilt in a given area. My Voyager has a 17" throat and I have had no trouble rolling an oversized queen on it using Warm'n'Natural batting.
It would help if you could narrow down a list to the specific machines you are considering. Every machine/frame setup seems to have its own quirks.