2 "next" buttons on check out

Hi,

They are not the same. The first one is the button to submit the registration / guest form of the "login" view.
If you have many views on the step, only the login view will be processed by it. It's quite useful, especially on a one page checkout where the login view is near the top of the page. Without it, after filling the registration form, the user would have to scroll down to the bottom of the page to find the button to submit, and he would likely miss it.
The second button is the button to go to the next step and it submits all the data on the step at once.
Now, saying this, if you only have the login view on your step, then both will effectively do the same thing and thus only one is useful.
That's why, if you edit your checkout workflow in the HikaShop configuration, you can find the setting "Show submit button" in the "Login" view. Turn off that setting, and only the second button will be displayed.