Question: Why would I want corded over cordless?

Answer: Long term use; I expect the device to sit in a box most of the year until I need it. I figure that this usage pattern is not the best to keep those batteries happy.

Question: Why flexible shaft option?

Answer: In the unlikely event I need a lighter handle to do the work. This would also be a ding against battery powered devices due to the extra weight hit.

Foredom has some real high end hardware. If I was doing fab work I could see putting that one high on the wish list.

Why Dremel?

Attachment heads that offer good price performance and wide selection of options.

For larger objects I would get a 10" buffing wheel for my lathe, or get a dual head buffing station.