I've dove them both.
The 905 was like diving a DUI TLS - which is to say, didn't stretch, really - except the 905 didn't have the telescoping torso of the TLS and was difficult to bend over in. It's easy to pull on and I loved the welded seams, which just exude the "I will last forever" aura.
The Fusion has amazing flexibility, and is by far the easiest drysuit to "fly" that I've dove yet (the bubble just meanders around and is easy to control). I was sceptical of the durability at first, but after 800ish dives on my original suit, it turns out the double-layer system really can take an amazing amount of abuse. Pulling on the suit can be a learning experience at first, though. And the crotch will droop down when you're walking around on the surface interval, kinda like "Gangsta Pants". Did I say that the Fusion has flexibility that has to be tried to be believed?
Make your priorities and pick from the strengths that match. Briefly, the 905 is great on the surface; the Fusion shines when underwater.
All the best, James