Well that is definitely less intrusive than I had imagined I still think that a HOB filter with floss/carbon plus a HOB skimmer would give you a lot more filtration capabilities. I can see the attraction for the AIO setup though as it would look more modern and you never have to worry about a potential overflow issue from the skimmer or even clogged hob filter.
I would be suspicious of the LFS store saying that the filtration would be far superior with the AIO because that simply isn’t true. HOB skimmers are made for tanks up to 100 gallons and HOB filters can be huge too. You would add additional water volume too with these options. I could understand if the LFS said that they preferred the aio because of aesthetics and no potential of overflow but to say that it’s filtration capabilities is superior is just wrong.
In the end both set ups will be cool and I hope you enjoy!