It'll be D2S.
I disagree with NickW on this one. As we've proved time and time again, the cheap Chinese shite doesn't last well*, and all egay stuff will be that tat. A branded bulb will be good for 10yrs.
*HIDs (actually all bulb tech, but especially HID) degrade badly over time. They still light up, and look bright when you look directly at them, but you will notice that the illumination capability is diminished. Or not in OPs case, if they have turned pink
. The process is gradual, and starts right from first use. There are crap bulbs, where this is highly accelerated, and good bulbs where this isn't.
I can also say, if they are the original, you *WILL* notice a difference. IME, most noticeable on a dark, wet night when bright lights are coming towards you.