I think UI5 has far more better look and feel . Many advantages in terms of User interface. Application is written in javascript, which is highly in demand in web application programming.
- SAP UI5 is an open source which supports technologies such as OpenAJAX, LESS, ARIA etc.
- The layout of the app is prepared with the use of HTML5 and CSS3, which provides flexible solutions dedicated to many devices and screen resolutions
- . Support of jQuery means SAPUI5 has no constraints concerning the
development of animations and effects - Open source libraries delivered by SAP allow developers to extend
existing UI controls (dialogue windows, charts, tables, buttons, combo-boxes,
data pickers, accordions) as well as to create new ones from scratch. To edit
UI controls a developer can use the ECLIPSE editor - The SAPUI5 technology supports the MVC (model–view–controller)
architecture pattern, which enables every programmer get well-structured and
understandable code - The prepared SAPUI5 application can be stored directly on a built-in SAP
web server or on open source platforms like Apache and Tomcat. It also runs on
various platforms such as SAP NetWeaver AS ABAP/Java, Sybase (SAP Unwired
Platform) and SAP Hana XS - SAPUI5 can work with the newest version of Sybase Unwired Platform
- Communication between a SAPUI5 app and the
SAP system is done through secure oData services - the newest standard prepared
by Microsoft. OData is proven secure technology which is currently used by
Facebook, eBay, Netflix and Stack Overflow. - SAPUI5 helps to increase your security
thanks to its cross-domain policy and indirect connection to the SAP server
through SAP NetWeawer Gateway, OData and the latest SUP (Sybase Unwired
Platform) - SAPUI5 enables the combination of multiple data sources such as oData services,
databases and external systems, as well as the data from multiple SAP systems,
all in one app
I hope these points will be helpful 
BR
Tejas