For a gaming laptop, is lenovo y50-70 good or should i go with lenovo y50? Which is a better option?

In all honesty if the Asus rog is within the same price, get the rog, better build quality and better screen quality.

If you can delay, be aware that 14nm graphics cards for laptops are coming out 2016 Q2 or Q3. Currently they are on 28nm and haven't gone down sizes like the cpu does. This halving of size will improve graphics speeds by over 10 times or reduce power consumption by 90% for the same size card. You will be kicking yourself if you buy one now. (google: 14nm graphics cards)