I have a Nikon Prostaff Spotting scope. Great optic for the price. It's lightweight, sharp, contrasty, performs well in low light, and is in your price range. I can see bullet holes on cardboard at 600 yards on overcast days. I've used it for hunting the last 3 years. Nikon's customer service isn't the best though. The tripod mount stripped out and Nikon was going to charge me to have it fixed. I complained and they fixed it for free. It took 4+ months to get it back.
I've never looked through the Bushnell Excursion so I can't give you a comparison. However, I've heard good things about them and had really good luck with everything I've bought from Bushnell. Their customer service is top notch. I lost a turret screw to a scope. I called them to order a replacement and they sent it free of charge, even after I told them I lost it. It was in my hands 3 days after I called them.
I'd find a store that has both and take them outside and compare them side by side.
If the optics where equal, I'd go with the Bushnell.
If you where to up your top price just a little, I'd take a serious look at the Nikon Fieldscope ED50. The optics are very impressive and it's ultra light and small. It weights 16oz compared to the Bushnell that weights 48oz.
There's a store on ebay that sells one for $550. Here's a link to their current auction: Nikon Fieldscope ED50.