Well I have been using zomato recently and have had ordered food a couple of times. And from personal experience I can tell you that its service is not good. My reason for saying that is listed below:
It has less restaurants and food stalls listed as compared to swiggy.
After placing order it takes more than 45mins to deliver maximum number of times.
Sometimes its app gets stuck.
No good customer support.
Once the app got stuck after ordering and the accepted order was cancelled of which refund is still in process.
Only few outlets delivers to my residence altough it being in the main city market area.
There are few positive things also:
Great offers from zomato.
Cheaper price than swiggy.