Is it better to wait an till ground for planting seed the next day AFTER it has rained all night?

or is it better to wait a another day? if tilling in compost dirt to clayish dirt to rake out and then plant fescue seed and starter fertliser..which is better and why? how different if wait 1 more day? and why some say you want it to be dry to till ..while others say you want it to be slightly wet or moist? which is true and why the contradiction maybe?