Lefevre Henri? Now that's definitely a person I've never heard of before. However, reading up on his wikipedia page, it claims that he was a Marxist Philosopher. A similar link also points out that he writes from a Marxist view. This is extremely common for historians ever since yonks ago (about mid 19th century) who gave a scientific, and rational breakdown in most things. In a sense, this logic was also applied to the French Revolution - so it is safe is assume that Henri would carry out (I'm generalising here) traditional marxist views, where the revolution occurred in stages, etc.
Simiarly, George Lefebvre is also a very common and famous Marxist historian - in fact, I thought you were referencing him the moment you mentioned him.
The difference between the two? That'll take deeper reading to be actually find an apparent difference between the two. However, given the constraints of time you have in VCE, it'll be fine if you just mentioned both historians by their similar respective views.
Some quotes I found for Henri is from this:
http://quizlet.com/20891675/historians-quotes-aos1-french-flash-cards/Henri states that the 'ultimate cause of the Revolution was the rise of the bourgeois'. I won't be surprised, he is a Marxist, afterall. Meanwhile, George Lefebvre would be similar in dictating such views. Similar quotes can be found on this thread:
The French Historiography Thread! and a breakdown:
https://suite101.com/a/review-of-george-lefebvres-the-coming-of-the-french-revolution-a345227