Which path is better for LYNC 2010 A/V performance among MPLS vs Plain Internet

Hi,

Please let me know which path is better for Lync 2010 A/V performance among MPLS or Plain Internet.

we are using good bandwidth internet Although 

LYNC Users experienced jitters,  lag and delay while communicating via LYNC call. FYI…Issue is intermittent

please any one suggest.

Thanks!