High-resistivity p-type silicon has emerged as one of the most promising materials for the finely segmented detectors to be used in particle physics experiments where high levels of radiation damage are expected. Beside the standard high-purity float-zone (FZ) silicon, relatively high-resistivity magnetic Czocharlski (MCz) is now available from industry. This material has been proposed as possibly more radiation hard than the standard FZ. This work shows a comparison of these substrate materials in terms of charge collection efficiency measurements performed with 40 MHz analogue electronics, before and after irradiation.