1.5 hour layover versus 6 hour layover at Guangzhou airport

I'm looking at two tickets Seoul to Delhi which transfer in Baiyun Airport. One has a 1.5 hour layover, the other a 6 hour layover. Though 1.5 hours is short, I'm wondering if it's too short to connect to my next flight (I found that China Southern tends to have late flights also). Also is 6 hours in the city too crazy??