Traffic, no question. DR is a metric created by a third party tool, traffic is Google actually sending people to that site. One tells you what Ahrefs thinks, the other tells you what Google thinks.
I've seen DR80 sites with 200 monthly visitors and DR30 sites with 50k visitors. The DR80 site got there from old links that stopped passing real value years ago. The DR30 site is actively getting crawled, indexed, and trusted by Google right now.
When I evaluate a site for a link placement the first thing I check is the traffic trend graph not the DR number. A site with 15k traffic growing month over month is worth more than a DR60 site that's been bleeding traffic since 2023.
DR has one use — as a quick filter to remove obvious garbage. Anything under DR10 gets skipped without looking further. Above that, traffic and relevance decide everything.