Is it better to wear wool tzitzis? indicates that it is better Halachically to wear a woolen Beged with woolen Tzitzis. Recently I met a fellow who the entire week wears cotton Tzitzis, yet on Shabbos ...
In the response to List of Techelet Wearers it mentions a few Gedolim that wear Tzitzis of Techeiles on Shabbos only. Why would there be a difference between Shabbos and the rest of the week?