I use both expired and auction domains, and they both pass juice.
Expired are cheaper but it might take you a little longer to rank due to having no age (potential sandbox).
Auction domains will be more expensive, but I prefer them because you can build your site (and more backlinks) quicker.
If you're just starting out, go for expired. If you have cash, auction. Sometimes the decision comes down to how nice the domain name itself is. Occasionally, I register fresh domains because the name itself is brandable or exactly what I need for the project.