I always use
align in my documents, and avoid
equation. Is there anything wrong with that? My reasoning behind this: align > equation, so why not use it?
While not exactly a bad idea in principle, unfortunately it is a bad idea in practise because
You should easily be able to see the extra space after the second ‘hello’.
Will all due respect to Will Robertson, actually I think that it is a bad idea in principle, because they mean different things and markup (be it *TeX, HTML,...) should be logical as much as possible.
If you are typesetting an equation, then use
You can decide easily whether you are typesetting an equation or not, by thinking how to want to reference it. If you only want one equation number to be displayed and see yourself suppressing by hand any additional equation numbers, (say by using