Performance - Stored Procedure versus inline

I am testing the time by putting each in this loop:

declare @loop int, @time datetime;
set @loop = 1000;
set @time = getdate();
while @loop > 0 begin  
    exec (@sql);
    set @loop = @loop - 1;
end
select datediff(ms, @time, getdate()) 'Delta';

Re calling stored procedure directly, I know. But for my requirements I need to call it via an EXEC since it is being invoked from a CLR routine.