My DiDi thoughts:

Long distances, such as to the airport, I generally do Premium, the usual home to work or restaurant run I take Didi Express or Select. Between 7.00 AM and 9.00 AM and 5.00PM and 10.00 PM and on Fridays and Saturdays in the late night it becomes harder to get a Didi. The surcharge system does not help much. Uber was much more aggressive in charging higher surcharges, and the chance to get a car in those situations was much better.

I am also very relentless complaining about Premium drivers to the customer service, if there was something I don't like, e.g. charging extra fees without informing me or providing fapiao for it or almost falling asleep and slowly moving into the adjacent lane. I got real furious once while I was travelling with my kids to the airport. Funny enough, sleepy drivers happened to me mostly in the morning like 7.00 or 9.00 AM.

But in general I think DiDi Preimum drivers drive quite careful. For Premium you also get a bottle of water. Especially arriving at an airport, rushing to the pick up spot, it is a nice little add-on.

For taxi drivers, I had even more experiences with sleepy drivers. But complaining there to the hotlines is useless.

Normally I find Didi drivers are driving more careful, less heart attack likelihood compared to taxi drivers. And that also goes for Didi Express or Select drivers - after all it is their own car. On the other side, I agree with synthkeys that they are less familiar with the roads, although in a city like Shanghai taxi drivers also do not know every corner and shortcut. In Guangzhou they usually knew the streets better.

In some cities I always use Didi, because I am just fed up with the taxi drivers there. Especially in Tianjin I had more than half of my times the experience, that they tell me some BS about the meter is broken, and they have to charge higher, there is a airport charge of 50 CNY without fapiao, or drive a really long extra route in the evening, saying there is less traffic - but then had felt like hundreds of red lights with each 2-3 minutes of waiting. Beijing experience is similar, although slightly different reasons. Some of the best experiences with Didi drivers I often have in very small cities. They are usually so overwhelmed that they can drive around a foreigner in their car in their town. Bit of Chinese helps wonders ...

Helping with luggage, only Premium drivers consistently help on their own. All other you need to ask to help in 90% of the cases. Some taxi drivers help when we are with kids, but I believe more because they are worried we damage the cars' interior when lifting in and out the buggy. Only exceptions are airports when there is supervising staff. I believe the drivers would get in trouble there, if they don't help.

As I have a local bank card, Didi is linked to my Alipay, so I cannot add anything in regards to foreign credit cards.

There are also other services besides Didi in China, which you can also use via Alipay app - but with English service I only know Didi so far.