Hi Mark and Wife ( I didn't catch your name on your profile),
Since you're interested in renting out both spaces long term and living in one of them short term, I would suggest going with a medium grade and quality material, with the lowest maintenance possible. Check out this 4 minute video from one of my favorite shows, Ask This Old House on stone countertop maintenance:
http://www.thisoldhouse.com/toh/video/0,,20504052,...
Host Kevin talks with an expert. If I were you, I would pick the engineered quartz. It has probably the highest durability and lowest maintenance of other stones, at a fraction of the cost of natural quartz. This is a surface you could live with and also impress potential tenants. A quick demo at each move-in on periodic surface maintenance could prolong the life of your investment. You could also do it yourself during inspections. It really is easy.
Just remember that higher quality finishes usually bring higher quality, longer term tenants and garner higher rents; not always the case, but more often than not. You should also check out the nearby competition. This will help you to not over-invest in finishes but still have a competitive advantage.
We would love to see pictures of your 1903 duplex!
John Newman