I've done many 1000's miles over the last 40 years using both.
Apart from the supreme ease of slow speed manoeuvring, faultless hill starts & the lack of clutch abuse whist doing both, the auto wins every time for uphill gear changes as there's no time lag to loose momentum. Under very trying conditions this can require two ratio drops, rather than one, whereas the auto is so quick only one ratio drop is required. These things are invaluable if (like me with a 1.6t 'van @ 50%+ use) a lot of towing is done.
Downhill engine drag is simply a case of selecting the correct gear, though I've always considered cadence braking the cheaper of the two options & use this in the main, in conjunction with either type of box (it helps if you have complete faith in you're brakes LOL).
The price is higher fuel consumption but, hopefully, no clutch replacement bill so this will help to offset it. I would prefer a manual during normal use though, if only for the (psychological?) sense of cornering control it gives.
The number of people I know that have changed to auto (for various reasons)
all insist (after a few months to get used to it) they would not change back; especially those that tow.
It's all about what you're used to, & what you find suites you & is more important personally, in the end.