What are peoples experience of sticky actions on the bottom of the browser and is visibility an issue?

I've been tasked with a project that is a careers site and there is some speculation on the need for a large button saying 'Apply now' sticky on the bottom of the browser like the attached image:

I thought it would be fine to do this at a vertical axis and smaller so it's not competing with other elements on the page e.g:

The problem is my colleagues think a big button is more prominent and obvious.

My question is what are peoples experience of sticky actions on the bottom of the browser and is visibility even the issue? As my colleagues suggest.