  We discuss cosmological hydrodynamic simulations of galaxy formation
performed with the new moving-mesh code AREPO, which promises higher accuracy
compared with the traditional SPH technique that has been widely employed for
this problem. We use an identical set of physics in corresponding simulations
carried out with the well-tested SPH code GADGET, adopting also the same
high-resolution gravity solver. We are thus able to compare both simulation
sets on an object-by-object basis, allowing us to cleanly isolate the impact of
different hydrodynamical methods on galaxy and halo properties. In accompanying
papers, we focus on an analysis of the global baryonic statistics predicted by
the simulation codes, (Vogelsberger et al. 2011) and complementary idealized
simulations that highlight the differences between the hydrodynamical schemes
(Sijacki et al. 2011). Here we investigate their influence on the baryonic
properties of simulated galaxies and their surrounding haloes. We find that
AREPO leads to significantly higher star formation rates for galaxies in
massive haloes and to more extended gaseous disks in galaxies, which also
feature a thinner and smoother morphology than their GADGET counterparts.
Consequently, galaxies formed in AREPO have larger sizes and higher specific
angular momentum than their SPH correspondents. The more efficient cooling
flows in AREPO yield higher densities and lower entropies in halo centers (and
the opposite trend in halo outskirts) leading to higher star formation rates of
massive galaxies. While both codes agree to acceptable accuracy on a number of
baryonic properties of cosmic structures, our results clearly demonstrate that
galaxy formation simulations greatly benefit from the use of more accurate
hydrodynamical techniques such as AREPO.
