I didn't mean the exact same sales, just they're pretty close. A 600k-1m difference in the US isn't that different (both systems were atomic bombs here), especially when you consider Saturn had about half the lifecycle Vita did.Saturn was an atomic bomb in US and Europe.
Even with PS Vita it can't compete outside Japan.
SEGA Saturn shipment:
NA - 1,80M
EU - 1,00M
JP - 5,75M
OT - 0,53M
Total: 9,08M
PS Vita case with ROTW is similar to PS2.
Sony ship a lot of PS2 in small markets during PS3 lifecycle.
This give to Sony a big domination on those makets and help PS2 to beat NDS.
Because in Fact in major markets, NDS beat PS2 by more than 20M.
Global reach has always been a big advantage with PlayStation over rivals like Sega and Nintendo. PS2 vs DS is a great example of that but you can also still see it today with PS4 vs Switch to some extent.