Great question — answering as the UphillTech team:
Both will target the same country automatically, it means you can't change the location in your search console, once you choose .pk or .co.pk , Google will consider you're targeting only pakistani visitors . So it is your choice to pick only one. There is no any SEO benefits or disadvantages. I will suggest first understand your audience, and then choose which you should pick up. I know Google are using .co.pk for pakistan and Google.co.in for India, but most of website like amazon now use .in for indian user, and most of other local eCommerce site also prefer to use .in because it is short and easy to remember . So first know your local audience and then understand what they prefer most?...
Full answer by Goyllo: https://webmasters.stackexchange.com/a/102445 (CC BY-SA 3.0).
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