A vehicle in orbit around the Earth has a good deal of flexibility when scheduling reentry. As long as consumables permit, they can easily delay reentry until favorable conditions permit. Having good crossrange capability makes things even better. You have the possibility - within reason - to reach landing sites that wouldn't be possible on a more ballistic trajectory.

However, as we consider the plans for going beyond LEO, most reentry flexibility is lost. Unless you have the ability to aerocapture into Earth orbit (long a dream but something no one has ever attempted, much less done), you have very few options about changing your reentry time and location as you return from the moon or beyond. You might be able to change your reentry time by a few minutes or hours by changing your Earth approach velocity, but given the narrow reentry corridors, there isn't a lot of room to maneuver. From what I remember, Apollo 11 & 13 had to shift their splashdown points somewhat to avoid bad weather, but their ability to do so was limited.

All of this leads back to Gary's point about a lifting reentry vehicle designed for the most rigorous condition (return from Mars) being a better choice than a capsule design. The Apollo capsule had very little margin for returning from the moon and wouldn't have any margin for returning from Mars.

Lockheed-Martin's CEV proposal appears to be some form of lifting body. Reportedly, it is designed to return from Mars with some reentry margin, so it'd have a greater margin for returning from the moon and reentry from Earth orbit would be a relative piece of cake. The lifting body design would also provide the potential for good crossrange capability, allowing it to have some options for landing sites to allow for bad weather at the primary site.