Not a fair comparison,...Eruption is a short instrumental piece for the sole purpose of showcasing Eddie's extraordinary guitar abilties.
Freewill is an exceptionally well put together song showcasing the talents of all it members, one the best Rush ever produced. It's one of my all time personal favorites. Geddy's tone and bass work are phenomenal...One of the reasons I play a Rickenbacker 4003 is to be able to nail that bass tone,....the Geddy Growl,...
But for the sake of answering the unfair question,...Eddie's solo is better, but Alex's song is far superior.