hi all currently riding carrera crossfire 1 which comes as standard with kenda 700 45's. after a blow out on rear it was replaced with a schwalbe landcruiser tyre foc which is 700 42. my question is should i replace the second kenda with the same schwalbe tyre or should i get a pair of 28's like the marathon plus?Would the speed benefit outweigh the additional cost? on a budget so dont want to spend silly money! thanks in advance for any advice