is there any difference in cds examination preparation and upsc preparation??

Both have different syllabus because requirements are different. Process selection is different. CDS wants strategists defence officers and Civil Service wants administrators.
Civil service is very difficult because it requires constant hard work for a year with the general knowledge of at least past 2 years. You can prepare CDS in 3 months if you're OK in elementary maths and good in English. Only portion which overlaps in GK, in CDS it is more about defence related questions and Civil service has questions from varied fields which are tricky.
If you want to Join Armed forces then only join CDS  or attempt CDS.
SO first decide your interest and then accordingly follow your interest and passion.
Good luck!