Short answer:
The Juggernaut is tougher.

Long answer:
The Power Tech has moderately better passive survivability but substantially worse defensive cool-downs/active survivability. In PvE the difference is not huge but in PvP the Juggernaut can take much more focused fire, especially if you are a hybrid spec Juggernaut.

Also although I know you said you do not care but its worth noting that the Power Tech is much better at getting and holding agro, particularly against large groups.