You should be fine with the spare if you have OEM tires/wheels sizes (whether 17", 18", staggered 19", or staggered 20", all have approx. same rolling diameters).

I had the Pirelli Scorpion Zero Assym previously and now on the Michelin Latitude.

The Pirelli are heavier than the Michelin, but does have a wider contact patch than the Michelin (even though they have the same width specs). You will be able to tell if you have both tires side by side. This is probably why the Pirelli grips better than the Michelin. The Pirelli also have better wear than the Michelin (I got about 25k miles out of the Pirelli, not sure I'll get 20k out the Michelin on the rears...both wore evenly). The Michelin, however, do ride more smoother and more comforable than the Pirelli. Given all these, I will most likely go back to the Pirelli for my next set. I was expecting better wear from the Michelin