This is one of those threads that could run and run, as it really comes down to personal preferences. Both series are fine, and have what you need. You don't need Vol 5 or Trevor Thom, but personally I think you do need the rest. There are less books in the Jeremy Pratt series because he has more than one subject per volume to a great extent than Trevor Thom.
I find Jeremy Pratt extremely readable, while Trevor Thom sends me to sleep! I find myself wanting to read the Jeremy Pratt books, while bored stiff by the Trevor Thom ones. I also prefer Jeremy Pratt's diagrams, and find his explanations clearer. But everyone's different. People have got PPLs for years and years using both sets of books, so it really comes down to which you prefer and how you like to learn.