Predicting the stability of coordination compounds using Crystal field theory

**The question is this**: 


On the basis of CFT, predict with justification which of the following two complex ions would be more stable [Mn(CN)6]4- or [Fe(CN)6]4-.


**Attempt at solution**: 


Both the complexes are low spin. Filling in the d electrons we get 5 electrons in t2g for Mn2+ and 6 electrons in t2g for Fe2+. There are no electrons in eg for both. 


Mn2+ has one unpaired electron while Fe2+ has completely filled t2g level. From here I was in a dilemma because Fe has fully occupied t2g level as well as a higher charge density because the effective ionic size of Fe2+ in low spin is 61 pm while Mn2+ in low spin has size 67 pm. However, due to Jan Teller effect the Mn compound will gain more stability due to the unsymmetrical filling of the t2g level. I know that Jan Teller distortion for t2g is less pronounced, so I was wondering if it was enough to make the complex more stable than Fe2+ complex?


