You'll get a lot of opinions...and mine. I'd go with the Leupold, the 40mm bell will do just fine, and you don't need the side parallax adjustment. As for what power, that's also delightfully debatable. Most folks are just fine with 3x9, but I'm not. Today I was shooting my 223 (6x18 VX2 Leupold) and having a fine time. Then I switched to my Dad's 223 NEF Handrifle with the 3x9 Zeiss Conquest scope. Compared to the Leupold, I didn't care much for the Zeiss (which was a surprise to me) and I sure didn't like the 3x9 power range. I'm used to seeing the bullet holes clearly and not needing a spotting scope to do so. That said, I'm a fan of the power range of 4.5x14. I have it in Leupold and in Burris. The Burris is less than half the price of the Leupold, but it is most definitely worth the money. The Leupold is better, but the Burris is still good. If you don't want to spend a lot of money, get the Burris 4.5x14 for $300. You won't be sorry. As for Nikon, they make great glass, but the Monarch I had wasn't up to Leupold VX3 quality and on top of that, it broke.
Now I've done it...I said bad things about Nikon and Zeiss. There will be H*** to pay now. But that is my opinion.