I say, and with God's guidance: Prayer is valid while wearing shoes if they are pure, but because of this, one cannot perform some of the Sunnah practices in prayer, such as the way of sitting in a spread position, and directing the toes towards the Qibla during prostration and sitting. Therefore, one would be considered to be committing a fault by neglecting the Sunnah, and it is disliked to neglect the recommended practices. Thus, one should only pray in them out of necessity, and God knows best.