I would, but it depends on the display. I find that it's a way to preserve the history of the airplane. So if that's the intention I would even display them together. But if if it isn't, then I still would collect them, but not display them together. Honestly I haven't, given it much thought. So I haven't checked for duplicate regs in my collection. I do know of a few that have had different regs but are the same aircraft.
I don't have a picture of both but for example, the 1:200 Aviateca 727-100 and 1:200 ALM 727-100 are the same aircraft different regs.
ALM is a resin cast custom and Aviateca (not my picture or actual model) is the one released by El Aviador models.
PJ-BOA as ALM and later TG-AYA as Aviateca. I might make OB-R-1135 as Faucett some time before ALM.