I read some online forums that Yizhong is slightly smaller, more interesting than Fengjia night market and also less crowded and touristy
Yizhong, night markets opens quite early, around 4pm. The shops opens much earlier and closes around 11pm to midnight.
Yizhong is definitely not as crowded as Fengjia. More space to walk around and the queue for food is slightly shorter. There is quite a lot of shops here, selling accessories and clothes. I bought a lot of stationeries.
Food wise, I think Fengjia has slightly more variety.
I don't have directions to here as I stroll here from my hotel. It is like 15-20mins walk but the directions were quite straightforward.
I went twice, once at night and once at the night afternoon.
Fengjia is definitely the one to visit. If you are staying more than a night, this is a good place to eat street food and shop.