I luv both but ill chose SIS as the best mobile base application.
Cuz.
Java ME is Ideal for a portable solution, if the Java ME platform provides the needed functionality. Good for vertical applications that must be portable. Device-specific libraries exist for many devices and are commonly used for games, making them non-portable.
While
Very powerful for general purpose development. The Symbian based S60 platform is strongly supported by Nokia with some support from other device manufacturers. In Japan NTT DoCoMo's Symbian based MOAP platform is also well supported by a number of manufacturers (Fujitsu, Sony Ericsson Japan, Mitsubishi and Sharp amongst others). It should be noted, however, that MOAP is not an open development platform. Another Symbian based platform, UIQ, is less well supported (principally by Sony Ericsson and Motorola). Currently large device deployments in Europe and Japan, with little penetration in the US market.

And in terms of Capabiltities, sis is the best cuz its Good on latest version, has many Many Widgets, Visual Form-Based GUI Builder, has no functionality No restrictions.
Enjoy guys.

i know i prefer symbian any day of the week and twice on a sunday