I was never a fan of "alternative" tab behavior in Visual Studio, and I'm not sure I like it in Firefox either. The saving grace is that the other keyboard shortcuts for changing tabs keep the original behavior, but still. It always feels like the tabs are a moving target when it cycles based on last viewed.
I like the behavior shown in this post. Currently however, I use Tab Catalog so ctrl + tab displays a visual representation of all open tabs in all FF instances. I think I may still prefer this as it makes it quick and easy to jump between FF windows seamlessly.