It is Cisco`s preferred choice as well as many SI`s now , I think it is up the individual however in my experience one of the main reasons to go with Device based CSS i.e blocking numbers is the reduction in the number of partitions and CSS required IF you have a cluster with offices, locations in different areas having GW and wanting their calls to go out on their local GW
Pro`s:
Single site
Limited number of Route Patterns, I tend to use a single PSTN route of 9.! and reduce the T302 timer for all calls
Common Partitions -Block Local, Block National etc - can be used in more them one location, Office regardless of the PSTN access code - 9, 0 ,X etc
Common CSS being applied to Users , Ease of support - CSS-BLOCK up to International - means block international calls regardless of where the user is located, what country etc
Con`s
Multiple sites- Need multiples of the Allowed PSTN pattern to route out on the local GW
9.! London
9.1 Manchester
9.! New York
Initially Harder to understand
Also you may have Service Desk ( SD) , Help Desk type number which are common in your company but need to be routed to the localised Service Desk`s - device based CSS works better as it is the location of the devices which routes the call rather then the user. EM users can log into different locations , dial the common Service Desk number but still route to the nearest SD to their, Device location
You need a full understanding of the dialling patterns a user makes as it is the user level which now blocks calls as the phone is "open" but I think this occur regardless of what CSS method you employ
