Mugen is a personal taste whereas OEM is most peoples taste
If its resale of bumpers only then mixed bunch and dependent on price and car (PFL or FL)
If its full car with bumpers most these days are looking for as OEM as possible, others may take a shining to it.
Alot of if, buts and maybes there but it really is that sort of thing, bit like Marmite really
Resale value wise Real mugen is worth more standalone