I read through the Hornblower series many times from age 12 to present. Read through Aubrey/Maturin once. Loved them both. Would not, on balance, compare one adversely to the other. Hornblower is an easier read (perhaps because Forester’s technique is less intrusive). Forester wears his erudition lightly.
Yes, Hornblower is neurotic, but easy to be fond of for all that. The Hornblower story arcs are relatively easier to follow and less bogged down with numerous characters - Forester seems to have happily struck upon the device of having an ensemble cast (Bush, Maria, Pellew, Barbara) which changes only relatively slowly so there is time to develop the characters. I contrast that with, for example,
the unsatisfactory way that Diana is simply written out in Aubrey/Maturin
I also found
the to-ing and fro-ing of Aubrey and Maturin’s financial affairs, and their relatively random resolution a little unsatisfactory
The stronger ensemble effect in Hornblower may be a consequence of the fact that Hornblower’s career is completed in fewer books.
And for mine, Aubrey’s villains can be a little cartoony. Hornblower’s Spanish opponent in The Happy Return, by contrast, is wonderful.
While there is nothing in Hornblower that is the parallel of Maturin’s devotion to natural history, Hornblower’s combination of intellectualism (devotion to Gibbon, etc) and physical courage suggests that Aubrey/Maturin represents (to some degree) a splitting of aspects of Hornblower into two characters, perhaps for plot-exposition reasons. And the splitting allows presentation of more extreme manifestations of the separated characters than would be plausible if combined in the one, as in Hornblower.
The wonderful formality of 19C manners is still present in Hornblower, although in a slightly different way. There is almost no overt sexuality. The sense of obligation and attendance to duty and concepts of honour feature in similar ways. The absence of slapstick humour is not a burden in Hornblower - he is no painfully humourless Thomas Covenant.
I read Hornblower in chronological order, as I did A/M. I was not troubled by the (relatively minor) plot hiccoughs this causes - it’s not supposed to be a John le Carre, after all.
I can’t imagine anyone who loves A/M not enjoying Hornblower.