Yes it would be the same as doing power chords - but - if you are harmonizing out of a scale it will not always be this way....
Lets take a look at a major scale (how about C?)
C D E F G A B C

the fifth above C is "G"
D - A
E - B
F - C
G - D
A - E
B - F

But the thing is.... a B power chord is B and F#
"F" is a flat five... which gives it a diminished sound (listen to "Black Sabbath" by Black Sabbath to get the idea)
When harmonizing from a scale, a whole new venue opens up.
But generally, fifths are not flat in the majority of the standard modes, so it aint that big o deal.