Hi Tourers

I'm wondering if anyone out there has travelled from Hong Kong to Shanghai?

My main query is whether to travel following the coast from HK through Fuzhou; or to ride inland instead and pass near to Nanchang?

Both routes seem a similar distance and I'm curious about if anyone has used either route and can comment on it in general terms. I'm not keen on hilly / mountain landscape and much prefer the flat roads!

Any advice would be appreciated.