Depends really on your need. If convenience of 3G Dual SIM android is a must for taking benefit of tariff plans or other reasons, then there is no other handset in the market at the moment which is as VFM + having all features as Mi 280. If Dual SIM is not needed, then the comparison is like this,
Mi280 has a dedicated GPU. Galaxy Y lacks any GPU.
Galaxy Y has 832 Mhz ARM V6 processor whereas Mi 280 has 650 Mhz. Y looks better on paper in this regard but won't make a great difference in day to day use. Plus Mi280 will make up with it's GPU.
Y has 1200 mAh battery compared to 1000 mAh of Mi 280. Y will have better battery life due to higher battery + Single SIM. If you'll use only Single SIM in Mi 280, battery life will be improved. Still Mi 280 battery life will be poor in comparison.
Both has 240 x 320 resolution. User memory also similar. Rest all mostly same.
Samsung is expected to have better component + build quality + service support compared to spice. But understand the difference in quality for such budget devices compared to Spice won't be so huge as compared to higher priced models. Samsung too is working within a budget and can't give you quality comparable to S II.
Hope now you're able to make the judgement yourself for your question: Whether you want to spend 1,500 more or not?