As far as your question, I would say neither. Think N+1, and think used. The two bikes are a 1987 and a 1992 (the 1987 Prologue has some significant upgrades, all nine speed Ultegra).
On my last hard packed trail, I took my road bike. It handled fine. I reserve my MTB for the crappy trails.
+1 Road bikes with drops are more comfortable. And much more efficient on pavement or smooth surfaces.
