If that's your reasoning, then it's strictly from a technical and intellectual level, rather then a solo that is built on any emotion at all, like David Gilmour solos.
I MUCH prefer guitar solos because the guitar is much more individually expressive instrument in the right hands. Most keyboard solos (I'm excluding Jazz, because key-solos in that style are essential and pretty freaking awesome) are annoying to me.
Mastery of an instrument isn't possible. But what is possible is mastery of what YOU DO on an instrument.
Most piano/keyboard players began learning classical or things of that nature. Those style of music are more technical based (as someone playing them, not as they were composed) learned by practicing for years and years.
Most guitar players started learning stuff by ear or tab or just strumming until they like what they heard. They still had to practice, but they sounded like themselves based on a ton of factors. Where they fretted, how hard they fretted, where they picked, how hard they picked.
Grab 100 seasoned guitar players and have them play the same song on the same guitar/amp setup. It'll sound different almost every single time. Grab 100 seasoned piano/keyboard players and have them play the same song on the same piano, and it'll sound very similar.
I do think it's harder to be as proficient as a piano/keyboard player then as a guitar player, but that is mostly based on the design of the instruments themselves.
I know I'm missing a few points on my side of this discussion, but I think I got the gist of it up there