I have a bunch of scopes that are used on calling rifles.
About all of them have the 50mm objective. The 50mm comes in handy in low light on higher power specifically.
I use the Leupold VX-III 4.5x14x50 Heavy Duplex, great reticle, easily acquired in low light. I have four of these scopes.
I also use a 3.5x10x50 Leupold VX-III Illuminated German #4 Dot, it has the 30mm tube and is an awesome scope.
I also use 1.5x6x42 Bushnell 4200 with the Firefly reticle on a Remington Model 600 .222.
The illuminated German #4 Dot is fast taking the lead in favoritism.