  As the theme for the future L3 Cosmic Vision mission, ESA has recently chosen
the `Gravitational Wave Universe'. Within this call, a mission concept called
eLISA has been proposed. This observatory has a current initial configuration
consisting of 4 laser links between the three satellites, which are separated
by a distance of one million kilometers, constructing a single channel
Michelson interferometer. However, the final configuration for the observatory
will not be fixed until the end of this decade. With this in mind, we
investigate the effect of different eLISA-like configurations on massive black
hole detections. This work compares the results of a Bayesian inference study
of 120 massive black hole binaries out to a redshift of $z\sim13$ for a $10^6$m
arm-length eLISA with four and six links, as well as a $2\times10^6$m
arm-length observatory with four links. We demonstrate that the original eLISA
configuration should allow us to recover the luminosity distance of the source
with an error of less than 10% out to a redshift of $z\sim4$, and a sky error
box of $\leq10^2\,deg^2$ out to $z\sim0.1$. In contrast, both alternative
configurations suggest that we should be able to conduct the same parameter
recovery with errors of less than 10% in luminosity distance out to $z\sim12$
and $\leq10^2\,deg^2$ out to $z\sim0.4$. Using the information from these
studies, we also infer that if we were able to construct a 2Gm, 6-link
detector, the above values would shift to $z\sim20$ for luminosity distance and
$z\sim0.9$ for sky error. While the final configuration will also be dependent
on both technological and financial considerations, our study suggests that
increasing the size of a two arm detector is a viable alternative to the
inclusion of a third arm in a smaller detector. More importantly, this work
further suggests no clear scientific loss between either choice.
