I think the Living Tribunal would win if the two fought...they both serve to play different but primal roles in their Universe. Besides, the comic just showed a brief cameo of the Tribunal, not the Tribunal being burned to ashes by the Phoenix or anything...
Living Tribunal - A cosmic entity that governs all the Omniverse to maintain a balance of order as it sees fit.
Phoenix Force - Is a cosmic entity that can bring out the destruction, and recreation at a multi - verse scale level as it sees fit.
Also The Phoenix Force being older than the Living Tribunal means nothing. Galactus is also older than the Living Tribunal. Or you could also say that Pre Recon Beyonder is younger than both the Phoenix Force and the Living Tribunal but is more powerful than both. Age really isn't a deciding factor when comparing their power.
Gender: Male Location: The Fortress of Solitude in Venus
LT - Is a cosmic entity that governs all of the muliti -verse to maintain a balance of order as it see fit. AND who can also bring out the destruction, and recreation at a multi - verse scale level as it sees fit.
PF- Is a cosmic entity that can bring out the destruction, and recreation at a multi - verse scale level as it sees fit.