Wing Chun = general English transliteration accepted by majority of people.
Traditional Wing Chun = William Cheung
Ving tsun = Moy Yat
Wing Tsun = Leung Ting
Wing Tzun = Emin Boztepe
Whats the difference? Well its allot of politics.
If everyone learned from the same person it should be generally similar... well in some ways it is. Allot of the general ideas you can see in all the of "sub-Styles".
My opinion of the differences:
Traditional Wing Chun = William Cheung:
1). He was a good fighter in his youth, but he relied on his natural abilities more than anything else. This is evident in his "style". He was pretty big for a typical HK youth. He chain punches WAY too much. He has added Chi Kung to his style.
2). Ving tsun = Moy Yat
Too soft, not enough hard. I can't comment on his training .. I don't know anything about it. Allot of people seem to just do things by blind faith, loosing allot of application... and basic ideas. JMO Do some research and find the real reason he spells it this way. Its pretty eye opening.
3).Wing Tsun = Leung Ting & Wing Tzun = Emin Boztepe :
Emin is a very VERY large person, and his style is VERY much influenced by his natural skill. That being said I have seen some clips were his chi sao has many good characteristics.
Leung Ting..

its amazing how he has the largest organization giving his background and training. They both tend to push the "blitz defense" and focus on chain punching and coming in. They tend to OVER train. What I mean by this is they will use too much force in training, at situations that are a waste of time. They have a “anti-Grappling” component to their style. (well emin does) It is mostly taken from his experience in Turkish oil wrestling. I have heard many times that they are training people for UFC and MMA.
So who do I “prefer”... I have come across some JKD people that are more Wing Chun that majority of Wing Chun schools. LOL
Sub-Styles I prefer:
Hawkins cheung, Duncan Leung, Lo Man Kam, Allan Lee.