It depends on how much control you want, medieval would have less control because that time period has already happend thus you can't decide what kind of tools and technology you have, future you can do whatever you want and let your imagination flow
A knight from king arthur's court in search of the holy grail meets fate in a snowy avalanche in the far north. Miraculously, he is preserved for a thousand years and is successfully revived to full health in the year 2525...