I own a 1-4x Trijicon accupoint with the crosshairs, as well as a 1-6x with Mil Dot reticle. Both are absolutely fantastic. They're lighter than optics with electronic components, I never have to think about batteries either. I remember the frustration with a red dot sight, getting out to the range, and the battery was dead and I didn't have a spare. Not fun.
The glass is amazing for the price. I also own a US Optics 3.2-17x, and honestly I can't tell a difference in the glass quality - not to my eyes at least.
I would say if you can afford it, go for the 2.5-12 x 42. Simply put, the magnification range is better (if that's important to you). It has a new generation light gathering system that in my opinion is superior as it presents a brighter dot, and is also easier to adjust. With the older version, the light adjustment is right next to the magnification, and turns in the same way so it's easier to grab the wrong ring and turn. You turn it and expect to adjust the zoom but suddenly the reticle illumination disappears instead. It's not a mistake you'll make after using it for a while, but it took some getting used to for me.
Also consider the 2.5-12x has a 30mm tube while the 3-9x only has a 1 inch tube. If you've already got 1 inch rings or 30mm rings, that may impact your decision.
The only fault I can find with these optics is that they don't offer a first focal plane version for the mil dot reticle, and the 2.5-12 doesn't come with exposed big tactical turrets. But for hunting, they're ideal.
