Bale seems to have his team built around him where as Johnson is needing to bend over backwards to even get a start. That's why it's difficult to compare them in my opinion.
However I do think Johnson is the more versatile and intelligent player, similar levels of technique while Bale has a ridiculous edge in terms of pace.
In this league any fucker with pace seems to be a star so I guess as a PL player Bale is better, however he'd sink in La Liga or Serie A. Conversely I think Johnson would be even better there.
In short, fucking difficult to decide as they're both class.