Difference between E. Rubin and Osiris

["Poe Lim" <phlim at iinet_net.au>]

Is there an easy way to differentiate between the two?

I purchased what's suppose to be a Rubin, but when it came, the leaves were
larger oval than what I'd expect from Rubin, more like the Osiris leaves. I
was assured it's the Rubin, and now that it has been in the tank for two
months or so, the submersed leaves are longer and less oval. The new growth
is certainly red, but as the leaves gets older, the red colour fades (not
entirely, but to just a reddish/brownish cast to the green). I know both
have new leaves that are red, but I thought the Rubin was suppose to stay
red.

Any positively identifying featured would be appreciated.

Cheers,
Poe
phlim at iinet_net.au