Is there any benefit for this app if you've already installed SoS in your whole deployment ?
I'd say they are complementary.
The two apps were designed to be sisters, which is why you'll note a similarity in the CSS used. The S.o.S app has only recently started to sprout dashboards looking at the full picture of a deployment (Deployment Topology, Distributed Indexing Performance, Index Replication), whereas that typically is Deployment Monitor's bread and butter.
I'd say they are complementary.
The two apps were designed to be sisters, which is why you'll note a similarity in the CSS used. The S.o.S app has only recently started to sprout dashboards looking at the full picture of a deployment (Deployment Topology, Distributed Indexing Performance, Index Replication), whereas that typically is Deployment Monitor's bread and butter.
I think "no" for Deployment Monitor. SOS is newer and has many cool features. Deployment Monitor is older and does less.
The one thing I have used Deployment Monitor for: to steal and tweak some of its searches for ad hoc use. In particular, I liked some of its searches around monitoring volume of data from forwarders. Otherwise, I haven't used it since about Splunk 4.1...
IMO, SOS is much more actively used and supported.