"su -" and "su" - what is the real difference?

[LeVA <leva@az.isten.hu>]

Hi!

Here comes a lame question yes I know, but I need to hear the 
experiences and opinions about this.
I've read thru a number of documents which described the differences 
between the real and effective user ids and I am now just wondering 
about this:

What is the difference (I mean in the "real world") between running `su` 
(getting a non-login shell) and `su -` (getting a login shell). Is 
there a security related problem with any of the invokings above? AFAIK 
the real and effective uids are always set to 0 after both commands.

Thanks!

Daniel

-- 
LeVA