If you have less SMP (1 or 2) server to install then you can go for unserved license model for production setup. Sybase also recommends to go for Unserved license model if you have less sybase products to manage. Only disadvantage is if product issue found then you can't simply install it in other machine, you must generate separate license file for the host id and license file has to be placed in server itself.
Served license does not required host id based licenses, but you have to install SYSAM server to manage served licenses. In this case, if issues found with SMP server, then you can install it in some other machine then you map the licenses from SYSAM server.
Refer the below link
http://infocenter.sybase.com/help/index.jsp?topic=/com.sybase.dc00530_0200/html/sysamug/BABFGHCJ.htm
I hope this will be helpful to you.
Regards
Yokesvaran Kumarasamy