As a participant/submitter, it's kind of a strange thing.
And it turns out that I don't always select my "best" photos for the contest. But more try to guess at what the tastes of the voters will be. So it turns out that selection, for me, becomes questions of "guess what the jurors are thinking" and "how will this display given inherent constraints of the various media".
For example, tho it's a "garden" site and presumably a "garden" contest, the best in show photos have been of birds a couple of times if I recall correctly. Don't get me wrong - they're stunning photos - and, if I recall, got my vote. But they're about birds - not gardens. Birds in gardens to be sure. But birds nonetheless. And even some of the category winners in the past few years have been more about the critter on the plant than the plant (of the category) proper.
In doing some looking at past winners, one of the things that I noticed is bunches or groups often do better than single blooms. So I'm more inclined to choose a fairly good picture of a bunch rather than a stunning shot of a single element. (That's assuming I had a suite of stunners to choose from...which is rarely the case (but doesn't obviate the broader point.))
Morgan mentions that he (she?) chose to vote for "container arrangements" in that category...which means I made a tactical error in my selections in that I chose to include some more natural containers this year rather than commercial planters with more conscious arrangements. Missed the boat there. And I'm not saying Morgan's wrong with the voting - art is a subjective thing and we all have different criteria. What I am saying is that I didn't "guess" properly in this case. And that much of selecting photos for the contest is about guessing.
Then there's the thumbnails. As people scroll through, I'm certain that many only look at the thumbnails and only click on those that look interesting in the thumbnail proper. If that's true (and I know it is - I've seen it), that means that if one were to post a stunning shot whose composition isn't centered on the subject, it's essentially out of the running. So that informs my selection.
Then there's the question of the viewing device. On a normal, desktop monitor, the viewer must scroll on a photo that's longer than it is tall (portrait mode), whereas the landscape photos show up beautifully upon clicking. However, with a phone, you're better off with the longer photos because they display well in the way that we generally hold our phones (vertically). So...what to do? Punt and try to cover both bases with a 1:1 (square) crop on everything? A subject-centered square crop to account for the thumbnail?
Then, because we can enter five for each category, I'll look at the suite of photos I've selected to ensure that I don't have five or a similar style or lighting or even subject (single vs bunch, etc.). Trying to cover as many spots on the roulette table of voting rather than splitting votes among five similarly-styled shots.
These are only a few things I think about when selecting a photo.
Don't get me wrong. I'm not complaining. I enjoy the contest and (every year) wish I'd have taken more time in the selection process - or even shot to some categories intentionally (I really didn't have any fruits or veggies to enter, for example).
And I'm not really sure what the point of this post is other than to say that selecting photos for this contest each year is a process itself. And an odd one at that (in my case). There are some inherent constraints here - as is the case with anything that is juror-ed.
Last note - and completely unrelated:
The overall quality of photos improves by leaps and bounds each year. I'm really impressed by a number of entries this year. There's some really inspiring stuff in every category. So many times I hear myself think, "wow, I wish I could do that..." In my opinion, in every category I've looked at so far, there are a number of photos that are arguably "the best", depending on the criteria and tastes of the voters. Just some fantastic work. Really neat stuff. And a lot of fun to participate in both as a submitter and a voter.
