In my case, the biggest thing is the sound itself. Last week during a rehearsal another guitarist showed up with a BOSS GT1000 I think. We tried several things and closely matched sounds, but the difference in tone was really big. My sound was somehow hi-def in all cases, more rounded, more bottom and top, clear and somehow always had more definition.
In addition to that - the flexibility that I have is unmatched. I pick exactly the components I want or sometimes tweak those to my taste.
If you’re traveling using a plane - it’s much easier to bring all your tones with you on a laptop. Then just rent an audio interface and any MIDI controller at the place where you have the gig and you’re all set.
You can have a backup ready to go. I always have one although I’ve never had to use it so far.
Having said all this - guitarists love to have a pedalboard so that’s the only real drawback at the moment. As you know I’ve built myself a box that I just power up and I’m ready to go, but take alook at this:
This could be smaller and lighter without the SY1000. One can just put a MIDI foot controller there with one or two expression pedals and a small, portable lightweight GP system could be ready. A spare computer can also be mounted there just in case.
It’s very hard to compete with a decent computer+decent audio interface these days when it comes to sound quality. These integrated devices, specially the ones on the lower end of the spectrum, simply don’t have the processing power or high quality AD/DA converters/preamps to sound nearly as good.
Those are my reasons, but I’m heavily subjective on the subject 