From my own experience needing several sites running in both different languages but also for different locales (eg. UK and USA) I've found running these as separate Portals gives the most flexibility and control.
That's simply because none of the sites are tied to each other for content structure, skin graphics etc. In the past I've also found the localisation options are really best suited to a single locale portal rather than multi-locale portals. There hadn't been a complete solution that would allow all the elements of a DNN website to be localised.
The last show stopper was the e-commerce modules for DNN. Though some will say they handle multiple locales, they do this somewhat poorly and sites then rely on exchange rate estimates etc... with only a single base currency available (which is not needed when using something like PayPal).
So having them as different portals has given me real control and flexibility over each.
With the content editing, I rarely use DotNetNuke modules other than
OpenWebStudio now. There are others such as XModPro that should also open up the options to you.
As the tabs/pages are completely independent on the different portals, I create SQL tables to associate them with each other. Then with OWS I create my own content editing where from any page when clicking edit the user will see the tabs for each language so it can all still be done from the 1 location. A little work involved but if you're planning to really get control over the beast that is DNN then it's well worth the effort.