IME combining the 2 is a bad thing. The Red Cherry Shrimp are more aggressive when going after food and won't hesitate to knock the smaller CRS.
I have both species but take care not to put them in the same tank.
RCS will survive in any tank as long as there are lots of hiding places and sufficient plant cover.
CRS need good water conditions, hiding places and shrimp friendly tankmates to survive.
Are you suggesting that the RCS had something to do with my missing CRS? As far as water condition goes and hiding places, everything is up to par.