Extreme Programming (XP) suggests replacing planned up-front design with evolutionary design, which advises implementing the simplest solution that satisfies the current iteration's requirements. However, the literature records several instances where development teams have argued for the naturalness of and need for, planned design. This paper describes two experimental studies that compared both approaches regarding product quality and programmer productivity. Results from both studies show that (1) difference of product quality, there is no significant independently of the subjects' experience, but (2) novices are more productive when allowed to use planned design.