More complex stored procedures are more complex to compile the SQL server correctly and execute quickly and efficiently.
Even in a large stored procedure, you need to either have multiple copies of the request, or add a lot of CASE and IF to it, which reduces performance. Thus, you do not really get much from combining everything together.
In my personal experience, I also consider large SQL code with a lot of branches, which are more difficult to support with several smaller and simpler sprocs.
UDF .
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