Why is DashboardClient taking so much memory on MBP?
Probably the widgets you are using are leaking memory. Try removing them and check which of the widget is taking too much memory. 

I use Calendar, 2 Clocks, 1 Weather and 2 Webclips and the Dashboard client is taking up 83Mb. Normally I just force quit if I see it is taking too much memory, and start it again if I need to them back.