Different latency setting in X1?

Hello All,   I just upgrade to X1 from 8.3 and find that I have to adjust the latency slider in the audio/midi settings section to a much smaller number.  If I don't, there is a terrible lag when playing the midi piano track with it's output set to Truepaino vst.   Does anyone know why I am having to make the adjustment when it was not necessary in 8.3 (which was also 64 bit)
 
I prefer a higher latency number as it seems to prevent the audio from dropping out when recording.  I'm using motu microbook and PC with windows 7 with all updates.
 
Thanks,
 
Michael

I just upgrade to X1 from 8.3 and find that I have to adjust the latency slider in the audio/midi settings section to a much smaller number.

That doesn't make much sense. For a given interface, driver and buffer size, the net latency will be the same with any VSTi host. SONAR itself adds no latency. Something else has changed. Maybe you're now running a convolution reverb that uses PDC, and trying to compensate for that by dropping your buffer size...?