MichaelT.

The same scope comparing a 40mm to a 50mm might give you one more power setting in the same light. In other words, if at dusk you can see something in the 40mm scope at 5 power, you should be able to see it in the 50mm at 6 power. Roughly said. And for that small gain, you really have to weigh out the difference in price, between the two, and see if it is worth it to you.

Also, I own 4 Nikon Scopes. 2 of them are 15 years old and work perfectly. I think they are about the best value going.