  We cross-match and compare characteristics of galaxy clusters identified in
observations from two sky surveys using two completely different techniques.
One sample is optically selected from the analysis of three years of Dark
Energy Survey observations using the redMaPPer cluster detection algorithm. The
second is X-ray selected from XMM observations analysed by the XMM Cluster
Survey. The samples comprise a total area of 57.4 deg$^2$, bounded by the area
of 4 contiguous XMM survey regions that overlap the DES footprint. We find that
the X-ray selected sample is fully matched with entries in the redMaPPer
catalogue, above $\lambda>$20 and within 0.1$< z <$0.9. Conversely, only 38\%
of the redMaPPer catalogue is matched to an X-ray extended source. Next, using
120 optically clusters and 184 X-ray selected clusters, we investigate the form
of the X-ray luminosity-temperature ($L_{X}-T_{X}$), luminosity-richness
($L_{X}-\lambda$) and temperature-richness ($T_{X}-\lambda$) scaling relations.
We find that the fitted forms of the $L_{X}-T_{X}$ relations are consistent
between the two selection methods and also with other studies in the
literature. However, we find tentative evidence for a steepening of the slope
of the relation for low richness systems in the X-ray selected sample. When
considering the scaling of richness with X-ray properties, we again find
consistency in the relations (i.e., $L_{X}-\lambda$ and $T_{X}-\lambda$)
between the optical and X-ray selected samples. This is contrary to previous
similar works that find a significant increase in the scatter of the luminosity
scaling relation for X-ray selected samples compared to optically selected
samples.
