which is better option RV college, Bangalore or NIT Allahabad in CSE?
NIT Allahabad hands down!
Don't get swayed by the location factor component. It nothing much to do with the placements.
Placements in India are mainly all due to Alumini contacts and by college Tag.
By MNNIT you get both. Since elstablished in 1952 and also the first NIT to provide CSE, its alma mater are well placed at the top notch positions in spectra of companies. Added that the NIT tag importance you'll get to know soon when you will be applying for Job switch.