WxJx has experience of both, having first used the Thom manuals a few years ago. For whatever reason I stopped pursuing my PPL at that time, until two years ago when I started again; this time with the Jeremy Pratt books.
I don't know about the latest Thom editions (so this may not be 'apples for apples'), but I do recall the illustrations being appalling! I was constantly having to to gaze at one or other of the piccies wondering what the hell it was that they were to portray!
What I do remember though was that the writing was excellent - clear, concise, economic and non-ambiguous.
The Pratt books are much better laid out in my opinion, benefitting from a modern, uncluttered design and (mostly) crystal-clear graphics. The textual content is also very good. Not conclusive I know but for what its worth I reckon you would probably be fine with either.
Regards and good luck
WxJx
