Historically, company A developed type A in the US, company B developed prt B in Europe, and each type succeeded on the market in its own country. Not related to any electrical reasons or so
Seems normal. What Halides are creamy yellow colored?
Actually there is one difference coming from the mains voltage (although a historical one).
It all started with MV's.
In Europe they were already reasonably efficient even when designed for the most efficient, cheapest and lightest ballast architecture of the time: A series reactor ballast.
However the US 120V was too low to allow any reasonably efficient lamp design, the ballast had to feature a voltage boosting capability, so the autotransformer and finally the CWA was born. And the OCV was about the same as the European mains, so about 220 till 240V.
Then move some decades later: The MH's were just an evolution of the at that time common MV, so it used very similar design. Just the fil was altered to add some components to reach better efficacy and color, even without the phosphor (so to allow to work also with a high efficiency of focused optics). So the Na-Sc chemistry was born.
But very early come a problem: With the typical 220..240V OCV there were too many lamps failed to start.
In the US the fix was easy: The common CWA ballast were just easily redesigned to an OCV around 300V. It didn't break the compatibility with the MV lamps, so it became a standard.
But in Europe that was a problem: A series reactor just can not deliver any other OCV than the supply it gets on its inputs. So first companies were trying different fill chemistries, but it all ended up with a need for something, that will boost the voltage for the start, so an ignitor.
Plus the 220..240V was rather low to keep the arc stable (the CWA has double the OCV available for current zero cross reignition, the series reactor has again just the mains voltage for that), so it would need a lower arc voltage designs, that means lower real power and greater stress for the existing ballasts.
And when an ignitor was a necessity anyway, it means the MV's can not be used anymore in these fixtures (they were not rated for the higher voltage the ignitor is capable to deliver).
And if the MV's won't be usable with the ignitor anyway and the ignitor was necessary anyway too, it was no deal to make the ignitor voltage way higher, going even into HV range and get rid of the auxiliary electrodes and so simplify the arctube design within the lamp.
And because of the simpler and more compact arctube construction being possible, it allows more even thermal distribution designs, opens the gate for way broader range of fill materials.
So a pulse start MH was born.
But the need for the igniktor was in fact a show stopper for the US market, when about similar performance was possible from the basic NaSc fill designs with starting probes and on the CWA ballasts.
And we have different design and chemistries between 120V and 230V markets...
