Old or new domain for new site - balancing factors?

Before I learned a lot about how things work, I bought some domain names that I thought would be good matches for niches that interested me. After learning a lot more, I recognize that my choices were more "seat of the pants" ideas than ones backed by search data. I have all the content lined up for a site in one of these niches now, and checking I found a domain name available that features the best search keyword in this niche. My dilemma, use my three year old domain that has just been parked in my namecheap account that is not a great match for the best search terms, or now buy and use a domain name that is a perfect match for one of the best search terms in my niche.

Your thoughts or advice please.

Are you talking about EMD or no? I don't think it really matters either way. Older domains tend to be better if they have been used in the past. If not, new domain is just fine.

Emd for low competitions/micro niche sites are awesome. You'll get some great rankings right away for the Emd keywords.
But for medium/high completion it's better to get a old and brandable domain name.

New domains will be fine if they are well optimized for SEs based on the competition they have, and new EMDs always work great for micro niche sites.