More important question, what's your price range?
For calling rifles, I like big tubes, and big objectives. A 44mm, 50mm, and 56mm objectives will capture a lot of light, and bring in a bigger field of view so you can see what you're looking at.
For coyote hunting, side focus is dang handy, but adjustable objectives can work just fine, just a little slower and a little more movement to hide.
300yrds isn't that far, but I'd still be looking in the 12-24x top end magnification (i.e. 4-16x, 4.5-14x, 5-15x, 6-18x, 6-24x, 5.5-22x, 6.5-20x, etc).
So, then you have to look at price range.
In the $200 range, maybe a bushnell banner. Great light transmission, clear optics. There are a few Weaver and Millet scopes in this ball park.
$200-300 ballpark I'd be looking Bushnell Elite or Nikon Buckmasters.
A great scope in the $400-500 ballpark is Nikon Monarch, some Bushnell Elite's, and Vortex Viper (standard).
Around $1000, Bushnell Elite 4.5-30x50mm is fantastic, Monarch high mags, Leupold VX-3 LRT's.
Around $2000, you're getting into Nightforce NXS territory.
Personally, I just picked up a Vortex Viper 6.5-20x50mm from Midway for $460. Great scope so far. Think I'll be getting another one in 4-16x50 for my deer rifle. No, they aint anywhere near my NF NXS 5.5-22x56, but for I can buy 4 of these VV's before I spent as much as one NXS, and for hunting, they sure work.