Rationale not to use Auto model 56 for all products

I could not understand why we should not use Auto model 56 for all Products .

I understand Auto Model 56 - checks for seasonality ,checks for trend , checks for white noise .

Lets say in what case I should use Model35 - seasonal linear regression rather than Model 56 .

Assumption: Performance is not an issue . I can afford the extra performance load on system by Auto 56