Prestashop is a dedicated ecommerce platform, while Joomla is a general content management system (CMS). That means a direct comparison between the two may not be meaningful.
The answers to a few questions might help clarify the choice in your mind:
Are you comfortable researching plugins and other add-ons to find "just the right thing" or do you prefer to purchase add-ons from a curated list?
Looks as though Prestashop offers a limited number of add-ons, many of which (but not all) you have to pay for. On Joomla, you will find a much wider array -- some paid, some free -- but you're not assured they'll all be compatible with each other so you'll have to do more testing to ensure your site works correctly with all
your chosen add-ons. Are you comfortable installing and testing plugins and other add-on modules?
Do you have experience working with open source software (and getting support from the open source community)? Do you already have in your contact list any Joomla experts (free or paid) you can reach out to if you run into a problem the community can't solve? Would you prefer Prestashop's approach of referring you to a "trusted partner" who will (for a fee) work directly with you to solve your issue?
In other words, how much of a "Do-It-Yourself" mentality do you have?