When your aim is as high as to become an IAS officer, ordinariness in effort does not work. You are required to take note of even simplest of the things. If your hardwork is not accompanied by proper guidance and support, you may reach failure very fast. In other words, a professionally competent institute can significantly enhance your performance in exams.
The reasons are as follows:-
1) Experienced and time tested teachers who can provide you with a broad intellectual disposition which is so essential for the exams.
2) A professional institute can provide you with research based study materials of good quality.
3) Apart from quality teaching, they are much better placed to groom you by way of test series programmes, performance evaluation and application of correctives etc.
4) A good physical and social ambience keep you motivated and focussed in approach.
5) Remember good teachers are costly but bad teachers cost more.
6) What A professional coaching institute can teach you in six months what no University can teach you in 2 years.
Therefore you should always join a good professional institute even if it costs a little more because you can gain in terms of time as well as intellectual depth.