This is possibly because its redesigned layout makes the words less cramped than previously.
The paper quality has also improved. That would be good for colour reproduction, which is good news for advertisers.
Also, the headings of the different sections looks more sophisticated.
This gives a more professional look to the paper. All these changes may not be so readily apparent to readers.
But it is still good for SCMP to make the effort for such changes which would help the paper to evolve and have a modern look and feel about it.
In terms of the main front news section, I understand that their editors would like to group both Hong Kong and China news under the 'National' section because of the territory's closer relationship with China.
However, I am not sure if this would be really that user-friendly to readers.
For those who really want to know what is going on in China, it would not be that convenient because they would have to scan through all the stories in order to pick-out China related news.
However, I do think that the 'City' section has been strengthened with the incorporation of more interesting articles and lifestyle topics. It makes it much more readable.