An E mark
means no doubt about the legality. So called +50, +80 etc just run hotter and output a slightly more focussed hot spot from a smaller burner (coil) running in higher gas pressure. Max benefit is about 15% in total output, but it looks a bit more.
My favourite legal bulb is Philips VisionPlus, a quality "plus 50" design. Hotter E marked bulbs have more light but also a MUCH shorter life expectancy, some will need changing as often as a rear tyre! Cobalt II get good reports on AutoExpress bulb tests and are cheap, but they waste some lumens in their blue coating and I don't think the quality is as consistent.
Away from E marking you can get 80/100 as eatscs says, which is a lot more lumens, and a normal life expectancy. However, it increases power in the wiring loom and connectors by more than 2.5x (P=I².R), which could cause trouble on some bikes. It also may be illegal in a good few EU countries, perhaps even here?