As both the branches are good but as per my view ECE is better to go for after B.Tech in Electronics. You can check the benefit of doing M.Tech in ECE below - As a Selection(screening) criterion in some of the Public sector organizations in the country (GAIL,HPCL,DDA,IOCL, BPCL, NTPC, BEL, NALCO). As a basic requirement for fellowship programs For obtaining financial assistance during Masters programs For obtaining financial assistance for Doctoral programs in Engineering/Technology/Architecture or other MHRD recognized institutes For obtaining financial assistance for Doctoral programs in Sciences' stream under MHRD recognized institutes.

Note : Before making any decision, kindly consider your interest and potential.

Hope this helps!!!!