It's basically Slim Shady Alter Ego vs Eminem/Marshall Mathers people think it's a new vs old thing cos The Slim Shady LP and The Marshall Mathers LP were predominantly Slim Shady Alias Albums predominantly where as The Eminem Show, 8 Mile Soundtrack, Recovery are Eminem Albums it's basically Slim Shady Alyer Ego/Shock Value Rap vs Deep/Introspective/Emotional Eminem/Marshall Mathers. It all comes down personal taste The Eminem Show is no different to Recovery even though they came out 8 years apart both are Deep Eminem while there is no difference between Slim Shady LP and Relapse both are Slim Shady and based on Shock Value.
For me i am a fan of Eminem/Marshall Mathers but not too keen on The Slim Shady Alter Ego.