I'm not sure that all offices can deal with foreigners, at least for Personal that isn't the case. The Personal office in Palermo, on Honduras, does.
I think we see Personal as being better for speed (I just got 80Mbps download indoors in Palermo now), but with smaller data packages, while Claro is slower (maybe someone can check what speed they see) but has enormous data packages.
For my Personal SIM I just add money to my account (Mercadopago, kiosk, or the recharging terminals), and buy 2 / 3 GB packages as required via text message, or the app on my phone.
Does personal have an app and the ability to buy prepago packs direct from a debit card? I was thinking about checking them out but Claro has become convenient to use during the pandemic. I'm also in the interior so it needs to work outside of BA