Well, with the Arai I ordered, I went just by their measurement chart. Naturally, my jug was just in between 2 sizes si I chose the larger of the two. the Arai XL cuts off at 24 inches and the XXL starts at 24 3/8. My head is 24 1/4 so I went up to the XXL. I fiugured I would rather it be slightly loose by 1/8 inch that slightly tight by 1/4 over the max in a size range. Worst case, I pull the strap.
Thom, if yours is pushing your cheeks up, it either means you have a really chubby face and/or you undersized the helmet. Is it tight around your forehead? Did you measure your head with a string and refer to AFX's size chart?
Here's their fitting guide and size chart to help you out.
Honestly, the Arai was a lot more money than I wanted to spend but a couple of things played into it. For one, it's a kick ass helmet with kick ass reviews. It has great ventilation from what I've read and is supposedly extremely protective and comfy. On top of all that, they had flat black which I particularly wanted so I can stop this helmet matching game I do.
The last helmet I bought was for my shifter cart and was an AGV. Retail was $509. Didn't wanna spend that money on it but chose it for most of the above reasons, protection and comfort being the highest. Honestly, that's the most comfortable helmet I've ever worn and was part of the reason I chose the Arai for my off-roader. Hopefully will be equal or exceed the AGV. If it does, it was worth the price to me.
Buster