Note: The following is not strictly on topic but rather theoretical, so it's not necessarily all too connected with whatever creative processes.
IMHO, scales and modes are more important than chords.
If you think about them on a "raw" harmonical or theoretical level, they're all the same, though.
And as this seems to be a rather trivial statement (for obvious reasons), IMO I think it's something worth to keep in mind, simply because it'll make plenty of things more efficient to deal with.
Just a few random things regarding that:
- Theoretically, each chord in a given key could contain any note in that key. You just keep adding diatonic thirds on top of your starting note (hence the root) until you're back at the starting note. 1, 3, 5, 7, 9, 11, 13 - and at 15, you went full circle (or rather two full circles, as it'd be the note 2 octaves above your starting point).
- Pretty much the same is true for scales. Just that you don't add thirds on top of the root but seconds instead. 1, 2, 3, 4, 5, 6, 7 - at 8, we went full circle.
- Obviously, the 2, 4, and 6 notes of the scale are the same notes as the 9, 11 and 13 of the chord. Sure, they're divided by an octave, but once we get into any real talk (as in playing those notes), we will bounce those buggers around by octaves around as we see fit.
- There's some "avoid notes" in chords (in quotes because there's no really strict rules, just to get that out of the way), typically creating dissonances (most notably b9 intervals, even if there's exceptions - see "no strict rules"). Such as the 11 on a major chord. Which is the same note as the 4th in a scalar context. Which is precisely why it's a decent thing to avoid that very 4th as a target note, too.
- Things get even more clear when you think about certain playing techniques. Blistering fast sweep picking of arpeggios - doesn't that rather sound like a chord than a scalar thing? Cluster chords played arpeggiated - don't they just sound like a scale played legato?
- The note D on top of a C root is a 2nd/9th, no matter whether you play it in a scalar or chordal context.
- Personally, I even tend to think of chords as modes (so to say) in case they're treated as an entity of their own (which is what modes are all about). Any Xm7/13 for me is a dorian chord. Any X7/9 is a mixolydian chord (at least for now and for the sake of this explanation, there's variations on both the dorian and the mixolydian theme, of course).
Oh yes, there's still some differences between chords and scales that are pretty well distinguishable (the borders are soft/blurred, though), but on a theoretical level, there's no differences.
Scales usually aren't strummed, chords don't make up for great melodies (but what if we harmonize those melodies? As said, it's all blurred...). So there's technical differences between them, even quite some. Still, once you're aware of the things they have in common, quite some things are easier to deal with, IMO at least (see "avoid notes" for example).