Looking for a red dot for my FNX-45T. I don't want to spend Trijicon RMR money. 

I've narrowed it down to the Viper or the FF3. I'd go Viper for sure but I'm concerned about how far out those side buttons stick.

Thoughts?

Put the Burris on my FNX .45 Tactical.  It's a well thought-out product and works fine for my purposes.  I don't know about the Viper's side button but it's not a
problem on the FF3.   The price was right on the Burris, as well.

They are the same price point. $190~230.00 depending where you buy it from.

The only major difference is that the Viper is 6MOA, and the FF3 is what, 3MOA and or 8MOA depending on model.

My Insight MRDS is 3.5MOA which dot size, seems to be just about perfect. The issue is I can't access the button as it's in the far back and the rear sight is in the way. My light and or the sun washes out my dot. The auto brightness isn't bright enough for me.