The domain in question has Moz DA of 80 with ~1,600 established root domains and ~25,000 total links. Domain is being moved due to a rebrand and there are no other options. Structure of the site will not change. Its a simple 301 from one domain to another.
The new domain options are as follows:
1) Premium domain used by someone else with Moz DA of 60, 700 linking domains and 20k total links. This domain has about 500 indexed pages and belongs to a completely different industry/topic.
2) Premium domain not used by anyone with Moz DA of 45, 1 linking domain, 35 total links. This domain has no pages indexed.
First question is which domain to move to. To me second domain means less mess to deal with.
Second question is what the impact will be. Lately there has been a lot of talk about how 301's pass everything to the new URL instead of "most" authority.
Biggest concern is losing the benefit of a ton of highly authoritative links in 90 - 100 DA range.