Hi Balajee,
In theme Designer, for every theme, there are different css properties(little changes).
For suppose, if you consider note taker, in eariler versions, the buttons in note taker are differently alligned in goldreflection theme and remaining themes i.e. platinum,etc..
If you don't have a problem with this, you can use theme designer.
Else you can create self themes which is good for you.
Regards,
Surendra.