On the chord difference. x46644 would be a C#m9, x46600 is a C#m7. Not sure where the disagreement is there, although the first one is a more common voicing than the other. I definitely have respect for those who can play all the chords without a capo or tuning, that's pretty tough. I usually go farther down the neck to find an easy way to play the more complex ones.

Yeah chris, there definitely is a difference in the different keys. You noticing subtle reasons why certain songs are written in certain keys? Other than how easy they are to play, or the major and minor, but a "feeling" to each one. The flat major keys are cool too, especially Eb, a very nice sounding key. B minor is an extremely dark sounding key and may need a little depression to feel it right. ;)

I like major keys even though I am a rock and sometimes metal player too. Major key’s don’t necessarily mean “happy” keys which is sometimes a misconception. Major key’s also have strength to them. Minor key’s tend to be softer on my ears. Something that doesn’t always work when your writing a tune that is hard hitting. A common thing to do with major keys when writing them in rock songs is to alter chord tones, like bIII, bVI, or bVII for example.

One thing I do also is if I write a tune that I haven’t really thought of an appropriate key for. I’ll write it in C major or A minor. It’s a lot easier to transpose a song from one of those than any other key. Usually if your write a tune in a altered key, it sounds too awkward when moved to another.