well in the desert i would recommend highly since i too live in the desert that you have in the rear no smaller than 20in on the rear and no smaller than 21in on the front. common size for desert racers is 23in on the front and 21in or 22in on the rear and a minimum of 6ply, reason for the larger sizes is to protect the under side of your atv from rocks and and also gives you bit higher top speed also the tires can absorb some of the terrain as well, remember the higher you go the wider you should go, and the more power it will require to get those larger diameter tires to start moving
to answer ur question now lol yes, you always want your front atleast 1inch larger so you have more control and optimal clearance and so the weight is centered mid to the rear, your back shock is designed to take the big blows while the front skip over the terrain also with weight distributed twards the rear you get maximum traction