Inspiration is in everything. Yet I think you're pointing at 'musicianship' which in my book covers a whole range of things. One of them being able to play a 'real' instrument.
I find the 'inspiration' of lying on your couch with a guitar at hand, your mind 'elsewhere', your fingers just picking away way more direct than consciously sitting behind my PC trying out things since the latter requires my mind to be 'present'.
I think this is the big difference.
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I think what the OP may have been trying to get at, in my interpretation, was that "live playing" a "traditional" instrument allows ideas to flow quicker and easier than using a mouse to draw notes on a piano roll which can be awkward and take longer. Much like using a mouse to draw a picture on a program like Photoshop or Paint is much more awkward than doing it with a real pencil on real paper.
I downloaded an app on my phone called Walkband, which is a piano/guitar/drum pad simulator. It's nice to sometimes just open that and play on the piano and out comes a melody. Happens much quicker for me than staring at a piano roll.
Got the Triple Play a couple months ago and it's response is just as good, in some cases better than the keyboard. I don't even route it through their vst or do the recommended separating out each string to it's own track. Just turn it on, arm the track and fly. Sometimes I do have to adjust the buffer and my system can handle more than average.
Anyway, it makes relating to whatever instrument is armed different but I don't know that it makes for 'more intimate' (?) because my roots are in playing guitar so of course it would feel better for me.
Music usually happens in my head first so it's not really a problem for me. Jamming on a guitar is a completely different feeling of course but when you space out and improvise like that you actually tend to do what you already know best. Experimenting new things on the guitar requires just as much focus and brainiac, er, -ness.
I wonder if making music with a guitar is much more close to inspiration than introducing notes in a piano roll.
If the person making music is more comfortable with playing guitar than using a computer, then, yeah, I guess it would be closer. But if they had never played guitar before, and they were used to using computers, then I think they would be much more comfortable with a piano roll.
Universally, I think it would be easier for anyone to learn how a piano roll works, than learn to play the guitar. But deciding which one would end up being closest to "inspiration" after days/months/years of practice depends on the person making the noise - what their preference is.
Inspiration is not affected by the tools you use. Your ability to take that inspiration and turn it into a product or a piece of art is. The more comfortable with your tools you are, the easier it is to translate your thoughts into the canvas, so to say. Of course all tools have limitations: Oil on wood does not have 'undo', photoshop doesn't work in 3D. You can't play chords on a piccolo flute, and you can't do vibrato on a grand piano. Or well, you can if you open it and manually tuck the strings.
Sometimes these limitations a particular medium has can inspire you, having to work around something to come up with alternative solution. This is mostly useful if your work is getting stale as you resort to the same solutions each time. Reatrictions breed creativity. New and different paradigms force a change in the mindset and forge different results.
The key is to get comfortable with the tools you have, and choose ones that suit you to begin with. This means not only your instruments, but the notation systems and musical forms as well. Guitar most likely feels more immediate to you because you are more comfortable with it than with your DAW.
Expressivity is another thing altogether. Different instruments allow for different forms of expression, and some certainly are more immediate than others. A DAW without a controller is pretty low on the immediacy scale. Guitar can be quite high. A MIDI keyboard with polyphonic aftertouch hooked in to a good softsynth as well. Continuum Fingerboard or the Linnstrument? Quite high.
For me, a textbook example of flawlessly integrating Guitar into electronic Music would be The Campfire Headphase by Boards of Canada, particularly the track 'Chromakey Dreamcoat'. The guitar isn't particularly complex but it melts nicely into the rest of the song.
The tools I'm stuck with are GarageBand and Audacity, and I play the odd bit of guitar over my stuff. Sure I could try and wrap my head around Ableton or Cubase. But I've gotten really good at GarageBand, despite its awfulness. Its limitations forced me to extensively explore the small amount of features it has, and I've developed a fairly unique, if somewhat Lo-Fi sound from that. So yeah. I think both comfort and adversity are the key to making Good music.