I am also thinking of time to change my Seat Covers. I also think that Rexine(which is usually called Leather hay Sir G) is a headache in summer days but only benefit is of easy cleaning, specially if u have kids so this will be easy option
Otherwise no comparison of comfortable Cloth type material...I am also thinking of making new covers in Light color(As dark color absorbs energy and get hot very easily) like Camel color or Off white or cream white color
First, get your seats re-foam with molty foam by process known as re-cushioning, it will take 3,000 to 5,000 depending upon your condition.
Over that,get your seat cover stictched with more Extra foam to give comfortable feel. It will take more 4,000 to 5,000