Oh man! This one is a HUGE topic to tackle. I don't even know where to begin. Choosing optics is like choosing underwear, It is a <font color="blue"> personal thing! </font>
I have tested just about every piece of glass known to man, and my research was so extensive on this subject, that I acually had to start a portfolio of information just to keep it all straight. I attended several optics seminars and kept all the marketing crap and all the "real" info that they don't give the consumer. If I had to sum it all up in one sentence, it would go something like this:
<font color="green"> Everyone's eyes are built with the same parts just like everyone's brain has the same parts, but we all use them differently and they give us all different results. </font>
The only way to really judge them for yourself is to look through them yourself.
We will have a Swarovski 20-60x80 non HD, a Leica Televid 20-60x77, several various Bushnells, and possibly even a Leupold 15-45x60 set up on our chuck hunt in several weeks. This would be an opportune time to view several different rigs in a real world (not inside the sporting goods store) scenario.
You will be the judge.
As for myself, I have located several different chucks sitting on top of rocks at over a mile and a half that were the same color as the rocks with my Swarovski. The only way I could tell that they were chucks is becuase that spotter has such great resolution (to my eye) that I could tell a difference in texture between the orange fur and the orange rock!
As for the physical aspects of the spotter, it totally depends on your hunting style and preferences. Personally, my 80mm Swaro is too big for taking Dall sheep hunting in Alaska, but is fine for mule deer hunting
in Utah. It absolutely is the cat's meow for spotting shots on chucks and gongs!
The angled eyepiece or straight is personal pref too. I find the angled eyepiece too slow for quickly picking up small moving vermin becuase it is harder to "aim" it where you want to look. However, it may be better for sitting and glassing a distant canyon wall for elk. But most of the time, I like a straight eyepiece for standing viewing.
I also love my Bogen pistol grip head because it is so rapid on aquisition, and there is no adjustment arm jabbing you in the throat all day. But others like the pan/tilt of a traditional head. It is all boxers or briefs my man!
Price is also a difficult Q. I would only say, "buy the best you can afford, and then go $100 dollars more!" I have lived off of Ramen noodles for lunch everyday for 3 months to buy the glass I wanted! It all just depends how serious you want to get.
Camera compatibility is nice, but unless you are a pro photographer, I wouldn't get too fussy about this. Just holding up a digital camera to the eyepiece can work good enough for most amatuers.
Zooms are best for unknown conditions, but getting a spotter with removable eyepieces give you the option of customizing a viewing preference in the field. A fixed eyepiece also has more field of view than a variable. Sometimes, I think it would be great to just have a straight 30x, and sometimes that is too much magnification. I thought when I bought a spotter that it would have to go to 60x no matter what. Now, I realize that there are actually very few times that I can actually use 60x because the mirage and loss of contrast become to much to deal with. A 15-45 is usually plenty.
Anyway, I hope this helps.