I am from Pilani campus, so forgive me if you find any bias in my answer but I will try to be as objective as possible.I think Roorkee and Pilani are in same category and Guwahati is little below them. ( you can compare all the colleges in various rankings in which on an average IIT Roorkee, BITS Pilani, IIT BHU compete for 6–9 ranks after IIT D,M,B,K,Kgp which are in a league of their own).
If you are someone interested in CSE, then definitely Pilani will be better than Roorkee but if you are not too sure about that, then Roorkee and the IIT tag associated with it will be beneficial in future. BITS tag in itself is not that well known abroad and even India for the typical Sharma uncles.
Now, coming to core subjects like Mech, Civil, Electrical,etc. I will be first to admit that we BITSians lack in technical knowledge to our IIT counterparts( because of ) attendance policy, more student friendly curriculum, lack of research opportunities, etc.)(please note that I am talking about average student from each college). But, placements is a different matter altogether. The scenario in core sector is bad everywhere but here’s where BITS has an edge with its flagship Practice School program: where many average students bag PPOs at top companies during college arranged internships and work there with top graduates from IITs who have come via campus placement route.