Light gathering capability difference between a 50 and 40 is night and day though...literally. To each his own. They'll both kill a deer, so to each his own I guess.
Wrong. Good glass and coatings trumps objective size every time. I own 50s, 44s, 40s and 32s. Did a test a couple years ago. Took a 50mm Leupold VX3 and a 40mm Conquest. Side by side, both rifles were in sand bags. Started looking through both at various distances and equal power at 5:00 pm. Both remained equally bright and clear within 2 minutes of each other. However I lost the reticle in the VX3 10 minutes before the Conquest. Back to Leupold it went for a heavy duplex. Turned a perfectly good Abolt 280 5/8 moa shooter into a 1.25 moa gun. Long story short, both were about equal in clarity and brightness well beyond "legal shooting light" whatever that is.
Hunted with a guy several years ago. He bragged about his new hubble telescope looking scope and how much "light it gathered". In reality it was an el cheapo Chinese made $75 POS. All I know is that guy was back at camp 15+ minutes before me every evening. BTW, that scope fogged internally and the warranty was worse than the scope.
