Inacoma is absolutely right with the comparison to Hoover.
There are 2 very distinct body styles, from 2 very different parts of Asia. Autorickshaws are the Indian style, totally different from Thai tuk-tuks.
The new electric autorickshaws introduced in parts of India and in Kathmandu (Nepal) in the past 5 years are a different style again, but I'm really talking here about the typical Indian Bajaj autorickshaw being wrongly labeled.
I've never come across anyone in South Asia - which comprises India, Pak, Nepal, Bangla Desh, Sri Lanka - who uses the word Tuk tuk. (I might be wrong, but I lived and worked in Asia for 10 years until 2003 and have travelled in all the above countries). 3-wheeled taxis are called an auto-rickshaw, or 'auto' for short. As I'm sure you already know, 3-wheeled commercials are neither an autorickshaw nor a tuk-tuk, but are called 'tempo' because the German tempo was the first major model, and more recently they are also called 'bajaj' as most of them these days are made by Bajaj. Just to confuse matters, some large 3-wheel taxis in certain parts of India are actually made by the manufacturer Tempo and these are called tempos, not autorickshaw.
In Nepal, I seem to remember all three wheelers apart from autorickshaws are called tempos, eg the larger Vikram 3-wheeler local buses.
4-wheelers have only very recently overtaken 3-wheelers as the predominant form of transport in India. ie there are so many more autorickshaws, bajaj's and tempos within India's 1 billion population, than in Thailand (population similar to UK) where tuk-tuks are mainly used in tourist areas of the large cities; i would estimate maybe only a few thousand exist in Thailand? Everywhere in Thailand the predominant form of local pasenger transport is by 4-wheel pick-up truck with a metal tilt on the back and a row of seats on each side.
There are no tuk tuks in China that I've come across, Witney. The only 3-wheelers I've seen there are roto-tillers (main form of transport in poor agricultural areas and all across Tibet) and sidecar outfit taxis in Kashgar (in the far west province of China). Lhasa also has cyclos (cycle-rickshaws similar to the Nepali ones). But China's a very big country and I've only travelled across; has anyone else seen 3-wheelers in China?
China has close connections with Thailand, but absolutely none with India (serious rivals; China invaded India in 1962; and India hosts his Holiness DL with Tibet obviously a contentious issue), so i guess it would make sense for a Chinese website to identify with a name closer to home - especially if it is selling Thai tuk-tuks to the West!
Re Jean's comment: Keith's 'tuk-tuk' page in Rumcars News quite surprised me as he owns one - but the heading gave the impression that 'autorickshaw' was the model of Bajaj; despite his opening paragraph that 'Bajaj is the major manufacturer of autorickshaws,' he described them otherwise in the article as tuk-tuks.
Yes, Blob, tuk-tuk is certainly the Thai word for them because of the sound they make, the same as 'tik-ai' is the name of the (beautiful) lizard that makes the loud call of 'tik-ai' during the night.
I'm not being pedantic just for the sake of it. And no offence intended to anyone if I'm speaking out of turn (ie you don't know me). But I am interested in club opinions of how important it is to correctly describe a vehicle type. Or at least to acknowledge that it has been mis-named. Otherwise, isn't it pretty much the same as calling a Peel a Reliant?