The Perfect Planner....this time new tire before Sunday's race

OK. In my typical fashion I'm trying something new just days( or less ) before the race.  This time it's not so much my own intention. I blew a tire for the first time just the other day and decided to order 'racing' tires.  Well, ONE of them came in and the other is still in transit.  WHY? Because one was on sale from one seller and the other at regular price from another.  Yes, this is indeed smart I know.  Anyway, enough self-bashing. I just replaced the blown tire (REAR WHEEL) with the VITTORIA OPEN CORSA EVO EX and left the front tire alone which has the Continental Ultra Sport. 

Will there be a considerable difference when riding?  I have not tested it on the road yet as it is almost midnight and I have to get up early to start packing for our family vacation.  But, I wanted some experienced opinions from others.  Go ahead and share your thoughts.

Thanks.