cj_iwakura
Member
Looking at first week Japan sales (main entries are bolded):
[PS2] Persona 4 (Atlus) - 193,000
[3DS] Shin Megami Tensei IV (Atlus) - 188,562
[PS2] Shin Megami Tensei III (Atlus) - 151,203 (Famitsu)
[PSV] Persona 4 Golden (Atlus) - 137,076
[PS2] Persona 3 - 116,682
[NDS] Shin Megami Tensei: Strange Journey (Atlus Co.) - 97,221
[PSP] Persona 3 Portable (Atlus Co.) - 94,287
[PS2] Persona 3: Fes (Atlus) - 90,369
It's not obvious that Persona is much more popular than SMT. Also note that both series sell more in Japan than in other territories.
That's great to know, but consider that SMT is a much bigger deal in Japan. It's got street cred going back to the NES/SNES days. It's only become really known here since Nocturne.