Xero and Quickbooks are fairly comparable accounting systems. I’m a Xero only provider so my comments will be limited to that.
To integrate Shopify into either systems you’ll need to purchase an add-on through the Shopify store.
If you have, say, more than 5-10 sales a day complexities can begin to arise in matching daily sales orders to the receipts in your bank account. If you have multiple payment gateways this can also add to the complexity.
Some of the add-ons, such as A2X, attempt to resolve this by “batching” daily sales into a single summarised entry – however since you want the sales and stock details to flow through into Xero they should be avoided.
Other options which provide the detail you’re after include “Xero Bridge”, or “Xero by OneSaas”, both have a 5 star rating – another similar add-on, “Shopify Integration by Bold” has only a 2.5 star rating so I’d suggest it should be avoided.
As you can see, there are a few considerations that go into ensuring that the system setup suits your requirements (and this will avoid headaches down the road) so you may want to get advice from an experienced accountant or bookkeeper.