I priced and ran benchmarks for my last server upgrade. AWS was 2x the cost of collocating and some outages around the same time. I think it would have been only marginally more expensive since I could scale my server down to current need rather than project 3-4 years into the future.
AWS had the fastest network and but colocation allowed for cheaper CPU and RAM upgrades. As it turns out, my RAM/CPU needs plateaued at 4x my previous server so I have twice as much as I need. AWS got steadily cheaper over that same time and the servers got faster.
Upgrading to a new server is pretty disruptive. It would probably be easier to do slowly over time rather than big jumps.
AWS had the fastest network and but colocation allowed for cheaper CPU and RAM upgrades. As it turns out, my RAM/CPU needs plateaued at 4x my previous server so I have twice as much as I need. AWS got steadily cheaper over that same time and the servers got faster.
Upgrading to a new server is pretty disruptive. It would probably be easier to do slowly over time rather than big jumps.