UCL is a product-specific entitlement while UWL is entitlement to a suite of products. If you purchase LIC-CUCM-USR you are buying entitlement for CUCM only with the following features:
Enhanced IP User License - Entitles the user to use of one (1) Enhanced, Basic, or Essential endpoint. The Enhanced IP User License also entitles Mobile Connect for a user. Any user with a mobile client or third-party mobile solution requires an Enhanced UCL.
UWL on the other hand entitles the user to a suite of products such as CUCM, Unity Connection, and Unified Presence. For example, if you purchased LIC-UWL-STD the user would be entitled to the features in Table 1 of this document:
http://www.cisco.com/en/US/prod/collateral/voicesw/ps6882/ps9156/product_solution_overview0900aecd806cc7a4.html
UWL is typically the recommended approach but it is not directly equivelent to UCL; the programs have different goals. If you are a partner additional information is available in the Ordering Guides.