Anyway I was bored so I went through the entire car list and these are all of the cars I would remove on the grounds that there is already another car in the list that is either exactly the same or so close to being the same I wouldn't miss this version.
Daihatsu MOVE SR-XX 2WD '97
Daihatsu SIRION CX 2WD (J) '98
Daihatsu STORIA CX 2WD '98
Fiat 500 F '65
Fiat 500 R '72
Fiat 500 L '69
Ford GT (No Stripe) '05
Honda S2000 (EU) '99
Honda S2000 (US) '99
Honda S2000 (EU) '01
Honda S2000 (US) '01
Honda S2000 (EU) '03
Honda S2000 Type V (EU) '00
Honda S2000 Type V (US) '00
Honda S2000 Type V (EU) '01
Honda S2000 Type V (US) '01
Lexus IS 200 (J) '98
Lexus GS 300 Vertex Edition (J) '00
Lexus SC 430 (US) '01
Lotus Esprit V8 SE '98
Mazda 110S (L10B) '68
Mazda Atenza Touring Car
Mazda Cosmo Sport (L10A) '67
Mazda MX-5 Miata '89
Mazda MX-5 Miata J-Limited '91
Mazda MX-5 Miata J-Limited II '93
Mazda MX-5 Miata V-Special '93
Mazda MX-5 Miata S-Special '95
Mazda MX-5 Miata VR Limited '97
Mazda MX-5 Miata SR Limited '97
Mazda MX-5 Miata 1.8 RS '98
Mazda MX-5 Miata 1800 RS '00
Mazda MX-5 Miata 1600 NR-A '00
Mazda MX-5 Miata 1800 RS '04
Mazda MX-5 '89
Mazda MX-5 J-Limited '91
Mazda MX-5 J-Limited II '93
Mazda MX-5 V-Special '93
Mazda MX-5 S-Special '95
Mazda MX-5 VR Limited '97
Mazda MX-5 SR Limited '97
Mazda MX-5 1.8 RS '98
Mazda MX-5 1800 RS '00
Mazda MX-5 1600 NR-A '00
Mazda MX-5 1800 RS '04
Mazda éfini RX-7 Type R (FD) '91
Mazda éfini RX-7 Type R (FD) '93
Mazda éfini RX-7 Type R-S (FD) '95
Mazda éfini RX-7 Type RS (FD) '96
Mazda éfini RX-7 Type RZ (FD) '92
Mazda éfini RX-7 Type RZ (FD) '93
Mazda éfini RX-7 Type RZ (FD) '95
Mazda éfini RX-7 Type RZ (FD) '96
Mercedes-Benz SLR McLaren (19inch Wheel Option) '09
MINI COOPER '02
Nissan PRIMERA 20V (EU) '01
Nissan SKYLINE GT-R Special Color Midnight Purple II (R34) '99
Nissan SKYLINE GT-R Special Color Midnight Purple III (R34) '00
Renault Sport Lutecia Renault Sport 2.0 16V '02
Renault Sport Lutecia Renault Sport Trophy V6 24V Race Car '00
Renault Sport Lutecia Renault Sport V6 24V '00
Renault Sport Lutecia Renault Sport V6 Phase2 '03
Subaru LEGACY B4 2.0GT spec.B '03
Subaru LEGACY Touring Wagon 2.0GT spec.B '03
Suzuki Cappuccino (EA11R) '91
Suzuki SWIFT Sport '05
Toyota ARISTO V300 Vertex Edition '00
Toyota CELICA GT-FOUR Rally Car (ST185) '95
Toyota PRIUS G (J) '02
Toyota PRIUS G Touring Selection (J) '03
Toyota VITZ F '99
Toyota VITZ RS 1.5 '00
Toyota VITZ RS Turbo '02
Vauxhall Astra Super Touring Car '00
Vauxhall VX220 Turbo '00
There are probably some more I missed, I didn't study it in great detail. But I'd love to hear any comments and reasons why it'd be a bad idea to remove any of those cars. Note that as I said before any regional variations (left/right hand drive) could be offered as as variation when buying the car if they've modeled it but not counted as a completely separate car.
There are plenty of other cars I'd also remove as they're not necessary but that's more my opinion so I left them off.
I'm not saying that they were right to include two versions, though I don't see why people hate it, when PD changes the name of the car.
Because it makes it seem like there are more cars to drive in the game then there are. If I owned a race track and invited you down for a day and said I had four cars for you to try would you not be a bit miffed if you turned up and I had a Mazda 6 touring car, a Mazda Atenza touring car, a Renault Clio and a Renault Lutecia? Extrapolate that scenario into GT5 and multiply it several times and that's why people hate it.