Larger tire size for Polaris 2006 450 help

Hello. We’ve got the stock Carlisle 489’s on our Quad – Polaris Sportsman, 2006 450. Everything on the quad is stock.

I’ve been looking at the ITP Mud Lite XL’s – I see they are advertised as a pretty light-weight tire. This should be good as we have the smaller engine, (450), and we are re-using the original steel rims.

I’ve got a couple questions.
First, they do not come in the OEM size for the rear.
The front OEM stock size is 25 x 8 x 12. They have that.
For the rear, the stock size is 25 x 11 x 12.
The XL’s only come in either 25 x 10 x 12, or 25 x 12 x 12.
Not sure which one to pick.

The other questions is more general in nature.
I thought about upgrading to 26 x 9 x 12 front and 26 x 12 x 12 rear, but I keep reading messages about using spacers, offset rims, clearance issues, etc. Once I buy the tires, it’s too late if they don’t fit right. Can’t send them back once I install on rims (of course).

So I started wondering. Why does everyone want to increase the tire size in the first place? I understand it will give more clearance, but realiztically, a 26 vs 25" tire will only lift the vehicle a 1/2", right?

Just wondering. What are the other advantages of increasing tire size to the point that modifications need to be made? I’m very tempted to stay with the OEM sizes, and run the quad as designed.

Any thoughts?
And again, any thought on getting 25 x 12 x 12 for the rear? That’s a 1/2" wider inside and outside from stock. Seems like it would be ok, right?