There are, as Andrew says, many subtleties inherent in metering. Chief among them, in general terms, is the "feel" that the meter generally implies.
For instance, in your example, if the top edit were metered in 2/2, it would feel much the same as the bottom edit. The difference is that the emphasis inherent in the beats of each time signature falls on different syllables in the music.
"1" is almost always the most important beat of any measure. Then, in meters that are divisible by 2, the beat that starts the second half of the measure (3 for 4/4, 4 for 6/8) is the next most emphatic. Other beats are usually less emphasized.
So, as written, your first edit would be emphasized something like:
ONCE a JOL-ly SWAG-MAN...
while your second one would be emphasized a bit more naturally:
ONCE a jol-ly SWAG-man...
if the first edit were in 2/2, it would usually be taken at a faster clip (up to twice as fast as you'd take it in 4/4), but the emphasis would remain much the same as in the first. However, a conductor, at his discretion, can instruct his group however he likes; He may tell them to de-emphasize the "2" of a 2/2-metered piece and you'd end up with something very close to the second edit in overall feel, but using fewer "flags" on the notes making the music "cleaner" and easier to read.