The fact of the matter is that the OEM lights only are street-legal, the others are not - this pretty much closes any debate on the technicalities.
The insurance companies love to avoid paying a cent if they can get away with it, both involved parties much the same, so good long looks would be taken into the safety-relevant equipment on both cars, everyone's breaths would be tested, paperwork checked and, generally, pressure would be kept up. Any claim, even if invented for the purpose, would be duly considered and in that setting the lights may be brought up by a party seeking an advantage: a 2-vs-1 game.
So this is not really about "bulbs or fixtures", it's about driver's responsibility, legal and otherwise.
Figuring out who will be the paying party isn't that hard at all, is it?