There is no fixed answer to this question. Prices on Swiggy and Zomato keeps on changing. And even offers also keep on changes Sometimes you can find the same cafe offering different prices on both the apps.
If you want to know on which one you can find the same food item at a cheaper rate then while ordering, check on both the apps after applying coupons. And then compare their prices. and order with the one which will be more beneficial for you.