I believe the issue is click tracking is being added to the links you hardcode into the email, but the ones that you put in via the variable in AMPScript are not included inside of the sweep that SFMC does prior to each send. This has been a bug that has existed for a couple years now inside of SFMC.
Both links should end up at the same place, just the one that has click tracking forces a redirect from another page first.
To prevent click tracking, you can remove the check from this box (Track Clicks) when you send the email (via wizard, user initiated send or trigger send) inside the 'Configure Delivery' section.
To have your links tracked when inserted as a variable, you should utilize Redirectto() or TreatAsContent() function calls.
Sample question on issue
Article about the issue