I have moved servers, workstations, and DAWs. Two to three hours sure beats the crap out of 2-3 days worth of installs. If you have a stable system, there is no need to re-install everything. Especially when moving a complex system, there is always the risk of missing something. A driver, utility, tweak, etc.
If you have a good clean stable system, just move it. On the other hand, if your system is a mess, installs/uninstalls/demos/crashes/malware/flakey drivers, then by all means start fresh.