I would think of the candidates as:
MTH z4k
Lionel ZW-C (with bricks)
Lionel ZW-L
They all provide fast fault protection. The ZW-L might offer an additional feature or two with fold-back capability, etc.
They all put out a good amount of power with the ZW-C offering the most potential, then the ZW-L, then lastly, the Z4K.
The Z4K has the best meters of the bunch.
I've owned the ZW-C and while it performed fine, it was not very robust from a feel standpoint. If manual control is the gameplan, I'd be concerned about it's handles holding up over time. Then there is also the concern about the internal board no longer being replaceable. I'd probably stay away from that one based on these points.
When down to the ZW-L and Z4K, I'd base the choice on brand of Command Control trains being used (now and down the road) as, for example, the ZW-L offers great benefit when connected to a Legacy command base in that it is controllable via. the Legacy remote. Essentially giving you four Powermasters to control track voltage.
