vQmod for .tpl files vs new theme

Can someone explain the pros and cons of using vQmod for .tpl files as opposed to creating a separate theme? I'm sort of feeling that the latter is simpler to implement and makes for more readable code.

Any views?

I prefer to build a new theme, so I can make a fresh looking instead of just modificate the default. Furthermore Opencart theme system have fallback function to the default, so build a theme with certain template you need is a good way instead of copy all default file to the new theme.

Yes, I'm familar with how themes work, what I was after was any views on why it's better to use vQmod or better to use a new theme to make changes to templates.