Both are great rollicking action adventures.
* Thomas is the uncle of the more famous Sir Harry Paget Flashman, V.C., whose memoirs are edited by George MacDonald-Fraser.
[0] https://robertbrightwell.com/my-books/flashman-and-the-seawo...
[1] https://robertbrightwell.com/my-books/flashman-and-the-emper...
there is an interview with O'Brian on YouTube.
(Don't ask for a link. Just search.)
I have read all 20 books!
Aubrey and Maturin are two of my favorite characters in all of literature. The depth of their motivations, their relationship, and their own personal wants are at the heart of the series. The best parts of the entire series are frequently their adventures on land rather than the purely naval parts.
As for the impossible naval jargon, I found it amusing to see the movie in (Danish) cinema, where the incomprehensible naval terminology was replaced in the subtitles with… incomprehensible Danish naval terminology.
I do like Hornblower. I've read all the books more than once, I bought the ITV show, and I even hunted down the Gregory Peck adaptation. To me Hornblower was a deeper character than I might have any right to expect in a historical adventure series, but his repetitive self-loathing in the face of his genius (genuinely a compelling choice) grates after so many books and so many successes and he begins to feel like a caricature of himself.
Like the grandparent, Aubrey and Maturin are my favourite characters in anything I've read. Everyone will tell you how they and their relationship is wonderfully depicted, but it could also have something to do with how many books there are and how often I've re-read them. At this point they're old friends so it'd be disloyal of me not to love them as much as I do.
I haven’t read Hornblower since I was a teenager, so some it might have gone over my head back then. My read on it was that it was more of an adventure story than anything. With the Master and Commander series I often find that the parts where they aren't at sea are the most interesting (The Fortune of War, The Surgeons Mate, Treason's Harbour are three of the books with particularly interesting periods on land). I am also biased since the subtle humor in the books is something I find particularly funny.
Not having read the Hornblower books since adolescence, I can't compare them, but on "characterization" : sorry, bro. O'Brian's the master of it. Two very good actors took on Jack and Steven (Russell Crowe and Paul Bettany) and made a classic movie.
Patrick O'Brien's books are too dry for me. There's lots of characters stopping and explaining naval terminology to each other, or long conversations about feelings and posturing and etc.
In comparison, Forester writing really captures the adventure and gives you the spirit of the era in much less verbose but sharper prose.
You can look a little further still to check out Dudley Pope's Ramage series.