Squiddy wrote:So within a Vortex are there more lenses or is the distance between the lenses and extended bell housing just bigger? What concerns me is that the Vortex glass would outperform the bushy at distance.
I don't have any technical data on the Vortex or the Bushnell so couldn't say, my response above was really just general information for your understanding in answer to your "why is the Vortex so much bigger" question.
This is getting more academic than practical but here it is anyway (short answer is go stick one of the scopes to your eye and see which looks best
).
Which has better "performance" though depends on design objectives and constraints.
e.g. larger front elements gather more light than smaller ones, a longer body allows for a longer focal length (more zoom) than a shorter one. All well and good, but, larger elements are larger (duh) and heavier, and lenses designed for longer focal lengths cannot focus at shorter ones... Great to look at distant things in low light, difficult to carry around and use to observe close or mid-range objects of surveying a wide area.
Smaller elements gather less light but benefit in size and weight, intending to focus on shorter lengths allows for a smaller build but restricts possible magnification... Great for carrying all day while you bust bunnies during the day, useless to see into the distance or through the gloom.
Once you're talking about actual scopes and not just design principles size alone basically means nothing.
What you see comes down to lens quality, quantity, arrangement, size, substrate and a handful of other factors not even touched on here.
A scope could be bigger because they are striving for more light gathering or increased magnification, or it could be bigger because to make it easier (cheaper to build) to build.
A smaller objective lense of better quality glass may gather more light than a larger one.
A shorter scope with a better designed lens arrangement may zoom further than a longer one.
High quality plastic may provide a better picture than low quality glass.
And 50 other theoretical this vs that scenarios we could come up with...
About the only thing you can get of a piece of paper to say one lense is better than another is light transmission.
Everything else you need to find a few that fit your purpose, hold them to your eye and see for yourself.