There is also a difference between multiple entry and double entry visas.
For Australian passport holders, the Chinese Visa options (last time I looked 9 months ago, and have been that way for years), are single entry, double entry, 6 month multiple entry and 12 month multiple entry.
To get a multiple entry (either 6 month or 12 month) you have to have has a previous Chinese visa and visited China on it within the previous 12 months. If you haven't had one before, or it was more than 12 months ago, then single or double entry is the only option.
Also beware if going the visa route, that the Chinese requirement for the photo is different to the standard passport photo requirement (and it changed about 18 months ago). Got caught out as partner's ear rings made the photo not acceptable, so had to do another one.
Other considerations:
Passport Real Estate - each Chinese visa of VOA (and not sure about TWOV) takes up a whole page - so using lots of them eats into space.
Wait times - depending on the time you cross (day, time of day, season), you can waste an hour or so getting the VOA (or you can be lucky and only take a few minutes).
Certainty - not likely to happen again, but during the Olympics, VOA was suspended. Never seen Shenzhen so dead and the touts so desperate. Having a Visa meant that there were no issues.
Cost - the Chinese Visa - single or double entry isn't cheap - the TWOV and VOA will likely end up cheaper, but there is a value to certainty of having the visa up front.
