Which is best between b.architecture and b.planning.

The duration of the course is different for B.Arch and B. Planning . B.Arch is of 5 year duration where as B. Planning is a 4 year program. The work nature is different for both B.Arch graduate and B. Planning graduates. The salary packages will be different for a B.Arch graduate and B. Planning graduate. The work pressure also varies for both professions.
Planning can be learned from below listed colleges:
Indian Institute of Technology, Kharagpur
Indian Institute of Technology, Roorkee
Lovely Professional University, Phagwara, Punjab
Bengal Engineering College, Sibpur University, Kolkata (West Bengal)
Visvesvaraya National Institute of Technology, (Deemed University), Nagpur (Maharashtra)
School of Planning & Architecture , New Delhi
Jawaharlal Nehru Architecture and Fine Arts Univ. (JNAFAU) under Jawaharlal Nehru Technology University, Hyderabad (A.P)
Maulana Azad National Institute of Technology, Bhopal
Sardar Vallabhbhai National Institute of Technology, Surat (Gujarat)
B. Arch. can be studied in below listed colleges:
National Institute of TechnologyThiruchirapalli
Centre For Environmental Planning & TechnologyAhmedabad

Architecture is the design of individual buildings.  Planning (assuming you mean urban planning) is the design of cities, towns and neighborhoods.  There is a bit of overlap between the two disciplines.  Planning may include developing architectural guidelines for planned neighborhoods, or building massing studies for large urban projects.  A large architectural project's design may be influenced by a variety of things that are previously thought out on the urban planning level.  Planning will rarely get into the smaller details of a building's design, and Architecture will rarely get into anything beyond the building's site.

Now it depends on you which interests you more