Would it be faster or cheaper to have a lander, SSTO, and/or SpaceX Mars rocket to rendezvous connect with a more efficient engine or "transport stage" or another lander, SSTO?
When the spacecraft launches from Earth the transport stage also breaks LEO headed in the same direction to meet out of orbit rather in orbit.
It is a question not so much about anything but the transport stage that is designed to receive different types of spacecraft? Is it worth having gravity and reduced travel time from engines that are more efficient but not yet not capable of launching from Earth or Mars to go back and forth from Orbit to Orbit faster?
The Orbital Mass Accelerator Engine Theory