The whole prog thing is so subjective as is every other genre and sub genre in music. There are many bands that it is hard to define a spot for because they cross so many lines. Rush is an example of that, a lot of their early stuff was long musical compositions that drastically changed directions multiple times within the context of the same song or on the same album. Some of what Rush was doing from 1975-1978 especially was kind of right in that ball park of say a Close To The Edge, Tales Of Topographic Oceans, Tarkus, etc. With the long segmented arrangements and concepts. The later work not so much.
The strange thing about Rush was they relied more on keyboards and synthesizers later in their career about the time they went in a more commercial radio friendly direction. Does that make them prog or not prog during the likes of Moving Pictures, Signals, Grace Under Pressure, and Power Windows, even Hold Your Fire. Roll The Bones I think was the last Rush album I purchased (and I passed on Presto). I'm one of those people that once a band's catalog has peaked and run it's course of the bands finest hour, and I then purchase a few mediocre albums It is hard to get me back into giving up my cash to continue buying. This happened over recent years with me with Deep Purple, with Yes, and it happened with Queensryche with Dedicated To Chaos. I viewed Hold Your Fire and Roll the Bones mediocre compared to the prior out put and stopped there.
But I love the bands early pre say 1990 work and I have everything I think from 74 through Roll The Bones minus Presto including the live stuff. I've seen them live post 2000 still a great live band.
My favorites would be
Rush
2112
All The World's A Stage
Exit Stage Left
Permanent Waves
Moving Pictures
Signals
Grace Under Pressure
Favorite songs: Working Man, 2112, Entre Nous, The Spirit of Radio, YYZ, Tom Sawyer, Subdivisions, Finding my Way, New World Man, Distant Early Warning