My basic interest is coding, so i only want to opt for computer science branch.I have two options in my hand one is CS at ISM Dhanbad and the other is CS at BIT Mesra. Which would be better and would be more valuable in future? Please help.

Computer Science is such a branch that irrespective of the college you pursue it from, you still end up in a good position. 

since ism takes students through iit-jee, so it always will continue to have a bit advantage over other colleges. and if it becomes and iit in the recent future (the ism to iit movement is going on and is in its peak stage right now), then a cs student from ism will be in a great demand. this year, the placement of cse in ism is quiet good and in par with older iit''s. neverthless, bit mesra also had a very good placement stats especially in cs stream. facebook visited both these colleges this year and selected 4 students in total. so if u ask me to rank them, it is quiet difficult but i would say ism will have an edge over other colleges.