IF ELSE vs CASE WHEN

The only explanation I can think of that 2 different project teams programmed it during the years.

There is no T-SQL theoretical explanation for it.

if exists(select name from sysobjects where name = 'myfunc') select dbo.myfunc()
else select 0;
-- 0

select case when exists(select name from sysobjects where name = 'myfunc') then dbo.myfunc() else 0 end;
/*
Msg 4121, Level 16, State 1, Line 1
Cannot find either column "dbo" or the user-defined function or aggregate "dbo.myfunc", or the name is ambiguous.
*/

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