Re: nikon monarch
Not more things to go wrong, and not quite fussy, just...annoying. To some. You have to turn the turrets twice as much for the same adjustment. And unless you are a benchrest shooter, you just don't need them i.e. if your gun can't shoot 1/8in groups, what good is it to be able to adjust in that small increments? Especially such close ranges. My monarch has them and I hate it haha But the other side of that, since you said out to 300 yards, it wouldn't be a big issue as you won't be needing to adjust very much. Another plus for the lower power is the monarch's have a horribly small amount of total vertical elevation. The 5-20 only has 34 minutes total. The 4-16 has 40. Still not great at all, but you might just need that extra 6 down the road.
The lower power is better for hunting, you don't have to search around as much to find your target in wooded areas/shorter range. And 16 really is all you need for long range if you so decide to got here. I'm a magnification whore, I like having all I can get haha So I know what you're thinking, you want more mag to see better and what not. But I rarely use it. Even shooting small prairie dogs out to 400, 500 yards (ok, missing them at 500..), I've notice I rarely turn the mag up past 18x, and usually it stays around 13x to 14x. I don't have a spotting scope, so the only time I crank mine up to 24x is to look at paper targets.