In my opinion you have a fine scope and there is no need to go to one with more power.  There really isn't that much difference between a 40mm and a 50mm objective lense and yes the 50 will let more light in than a 40 as long as you are on the same power multiplyer so as you go up to a 12 x power it will let in less light than it will at 9 x.  I have also found that for just about all hunting situations you don't need more than 6 or 7 power on a scope and most of the time 4x will do you quite fine.  The only rifle that I have that has a scope with more power than 10x is a .22-250 and it has a 6.5x20 but then it isn't a big game rifle. 

Like Critter said the scope you have is a good one. I don't have any with 50mm as I just don't like them that big and how much higher up they sit. When the scope says fogproof  I believe they are refering to on the inside. In bad weather you need to put something on the lenses yourself to keep that from happening amd maybe get some good scope covers.

Other than all that my next scope will be either another Leupold or the Monarch you mentioned.

Thanks for the info guys. Another reason I'm looking to upgrade is it's my dads birthday next month and he's had the same old Tasco fixed power scope on since around the early-mid 80's  and the clarity is just getting really distorted and after our Elk hunt in Montana this last season I took my first shot ever at an elk after 15 years of hunting (dad is at 20 yrs with never shooting at an elk) and it made me think that if my dad took the shot with his scope from that distance he probably wouldn't have even seen the bull in the scope so I figured since I got my scope only 5-6 months ago I could just get myself a new one and put my Nikon on his rifle for his birthday. So there's not really much advantage from switching from the 40 to 50mm? When I say I'm looking to get the 4x12 I'm planning on taking nothing but 350+ yard shots. I always had my Nikon between 5-7 during the hunt and might of gone to 8 when I shot at the bull. I just figured it wouldn't hurt to have that extra power if I ever needed it. But if the clarity just gets distorted at the high of power then I'll just stick with the 3x9.  What Leupold models would you guys recommend? I've seen some Walmarts carry Leupold scopes but not for sure on the model, but I'm assuming it's the Rifleman? Are those even quality scopes or did they just make those to compete with the lower market? I guess for my price range I'd be looking at the VX series. Which one of those models would work out best, or which one would you want out of those? And anyone recommend looking at anything else besides Leupold or staying with Nikon? I've had quite a few people tell me to drop Leupold and get that Vortex Viper and with the price on Camraland it's almost tempting! Anyone have experience with Vortex scopes or glass? Or have a different scope that they'd recommend?

Now that you've given a good reason then you you better move up. The scope I have been using foe many years now is the Leupold VX-3 3.5x10 40mm. This scope has been great for all conditions and comes in at about 479 right now. If you like some of the bdc reticles the price goes up and they are very useful for some hunts. The Nikon gets a lot of great reviews with the system they have and the online ballistic calculator.

There is nothing wrong with the 50mm I just like to keep a lower profile and have always been able to see with enough light as long as it was legal to shoot with the 40. I'm not to concerned with the field of view issue as with plenty of practice you will always be on the animal when you bring the gun up anyway.

Btw the NIkon monarch with bdc 2.5x10 42mm is is going for about 399.

Why not get your dad a new scope for his birthday? Where do you do your christmas shopping, 2nd hand stores?  Awful thoughtfull to find a good reason to give your DAD a used inexpensive scope for his birthday!   What will you get him for fathers day? Wait, used your old scope for a trade in and get your dad a card at the Walmart!

I'm sorry, I am a son and a dad!

Looks like you've got your answers, pretty much.

I just wanted to say that you should just try some out yourself, and form your own opinion. Because, as you posted in your initial post, different people will swear by diferent makers.

Guys will find their brand, and stick with it.  So, you ask a nikon guy who makes the best scope, adn guess what answer you'll get?  Same goes for Swarovski, Zeiss, Leupold, etc.

Heck, I'm happy with my Bushnells, and would recommend them to people. 

So, sounds like you're on the right track.  Sounds like a good present for your dad

I'm headin out to Cabelas and Sportsmans in just a few min to go check em out for myself!

Ok I came home with a new scope today. After comparing the Leupold vx-II and III, Vortex Viper and Nikons and having Cabelas be so generous by mounting a 50mm scope onto my rifle to show me the difference to a 40mm..... I went with the Nikon Buckmaster 4.5-14x40 with BDC rectile and side focus. I looked through all the scopes in low light conditions and bright conditions and they all seemed close to the same to me. What made me choose the Nikon over the Leupold and Vortex was my eye seemed to focus more quickly and easily with the Nikon than with the Leupold or Vortex and had a better eye relief. And 2cd was the price! The VX-II that I was interested in was $479.00 and the VX-III was $569.00. The Nikon was $319.00 and with all my Cabela gift cards I've saved up over my last birthday and christmas I got the scope and some buttler creek flip scope covers for $227.19 out the door.

Thanks to all of you who gave me the great info and your personal thoughts!