S4 Mini is well balanced phone. You see, it gives qHD screen with 8 MP FHD Recording cam, compared to HD screen of Moto G but 5 MP @720p. Its a Dual Core 1.7 GHz, a good and powerful processor with Adreno 305 graphics, same as Moto G(it got 1.2 GHz Quad). One of the best advantages is 4G, which you will really miss in Moto G.
Its a nice phone. Moto G is very much value for money, but if you can afford S4 Mini, go for it.
Look, best value for money phone: Moto G. Best phone amongst the 2: S4 Mini.