What is the difference between B.Tech after PCM and B.Tech after PCB?

If you have PCB in 11-12th then you can try for medical entrance exams. You can also look for bio-technology stream. You can try for exams like NEET, JIPMER and AIIMS. After PCM you can go for bio-tech if you have interest in biology stream, you can option for it even after PCB.

There is no difference, however, many universities/colleges require students to have a PCM qualification rather than a PCB one. A PCB qualification is preferred for a course in medicine.