If we talk about the brand value and worth of these two IIMs I don’t think there are many dissimilarities. The difference between the two is some personal level factors like

Campus: IIM Ranchi has no permanent campus and this is one of the major shortcomings of this institute. IIM Raipur on the other hand has a vast 200-acre campus. It is decked with world-class facilities and will give you the feeling of staying at a hotel.

Placements: IIM Raipur has better placements than IIM Ranchi and for many, this is a major deciding factor. The table below compares the placement statistics of the two IIMs.

Since the brand value of the 2 institutes is almost the same you can choose on the basis of the above factors.