Objective reasons to center or left-align tables and images within text columns?

Question

First, let me emphasize that while I am asking a question about preference, I am looking for objective reasons to prefer one answer over another. I am not interested in your personal, subjective opinion on which is better. I have no formal design training, so I don't know if there might any practical reason to prefer one style over another. That's why I'm here - to consult the experts, not incite wars of opinion.

Setup

I am part of a team working on a new design for our company's website, and the team and I have a disagreement over whether tables should be centered or left-aligned. If it boils down to a simple matter of subjective taste, I will defer to the team's preference. However, if there are objective reasons to choose one style over another, I'd like to be able to argue those points.

Here is an example of the alternatives:

Questions

1. Is there a generally accepted design rule when it comes to laying out tables and block images on websites?
2. Are there any objective reasons to prefer one layout over the other?

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Update

DA01 pointed out it can depend on context. My team also had this objection when I showed them this question. Here is an example that is more true to the actual site layout.

Answer 1

Are there any objective reasons to prefer one layout over the other?

Yes. But they're usually tied to context--namely the specific goals and type of content being displayed.

In other words, yes, one can find objective reasons to do it one way or the other, but it's going to vary based on the content, users, amount of content, type of tables, etc. And in the end, the subjective aesthetic reasons are likely going to out-weight the objective ones anyways...so I wouldn't sweat it.

(As an aside, for the small sample tables, I think either looks OK. If the tables are going to get much larger, I'd suggest considering left-aligning the data within the table to make for easier scanning of the columns).

Answer 2

1. I tend to see more blocky elements like that centered.
2. I would imagine there is an objective reason for each argument: left-aligned for readability, centered for balance.

But I think that centered makes more sense. You have a cavern of white space when you left-align the table, and if you study layouts you'll find that while white space is indeed a great thing, it's not great when it throws the whole page out of balance. And that's what centering does - makes everything more balanced because that white space is split up and equal on both sides.

In general, centering things can get dicey if you center too many lines of text. If you center a paragraph of text, it gets tough to read because your eye has a harder time finding the beginning of the line. But when you have a block element like an image or this table, that argument is diminished because there isn't as much for your eye to track. Your eye is first drawn to the entire block, and then there are neat columns inside that are easier to follow.

So, I recommend you center it. You have a better overall layout that doesn't sacrifice readability to get there.