Since both the the courses Physics and B. Tech would demand a lot of time and passion to excel well in the chosen field, you have to analyse your own interest before the perusal of either of the two.
Assuming that you have a flair for Physics, you need to choose a right institution where you get constant stimulation from your teachers and the environment should be conducive to sustain your studies. A high quality education in this area would be possible by choosing BITS Pilani or by taking Engineering Physics - a five year integrated course leading to a M.Sc degree in Physics. Later a doctorate degree in the same line can be achieved under the expert guidance of the eminent professors. Later, you can make your research career in ISC Bengaluru, Atomic Energy Commision Mumbai, ISRO etc. In all these organisations, you would get stimulating atmosphere to forge ahead in the research area with much enthusiasm. Salary- package, too, would be attractive. You may also join teaching profession, if you so like.
Now talking to the Comuter - field, if you have the drive and urge to learn different modules like Java, Oracle, C++ etc, this area seems to be the right field. However, you have to be innovative and result - oriented in delivering the tasks alloted to you especially in this time when we are witnessing a recessionary trend in the IT field. Lastly, you must be a product of B.Tech from a leading institution such as IIT where there is no compromise in quality in the different modules.
Hope, you would appreciate the points listed above.