Being an avowed Jazz Fusion man,I agree with your assessment of Rush.My initial thoughts: Pink Floyd adheres to more traditional rhythms, chord changes and rock-related passages. Also their sound is heavily orchestrated and about dynamics and textures.
Rush ventures into very atypical harmonies, lyrics and is closer to jazz flows, you really never know what to expect. Also, much more reliant on its musicians mastering rhythmic and melodic "fireworks", they are all virtuosos
That's why I was drawn to Rush and not Pink Floyd.
Which I found exceedingly depressing.