Congratulations! I've never won anything and to win something that one actually needs is awesome. I looked at both items. Hard choice! I might be more inclined to take the table only because chairs are very personal. I would want try a chair before I committed to it.
I have used a chair with casters on hardwood floors and actually I put one of those office chair mats underneath to protect the floor and help the chair to move even better. You can buy the mats specifically for hardwood. I really like having a chair on wheels, personally. I didn't have any problem with the chair moving around whilst sewing.