Both DU SOL and DU are very good institutes to prepare for UPSC and both of them have their own advantages. Let me share some facts I got to know from the reviews.

• DU SOL is an open learning institute where you will have to attend classes only once in a week, that too isn't mandatory. 
• You will just have to attend the annual examination and there is no other requirement for going to college. 
• You will get complete freedom whether you want to attend your classes or not and because of this some students get distracted from studies and thus are not able to prepare properly before their exams. 
• But it is beneficial for those students who are very sincere with their studies as they will get some extra time to prepare for UPSC and can also join a good coaching centre. 
• Sankalp coaching classes at RK Puram will be a very good option as it is very good and affordable. 
• DU is a regular university where all the students are required to attend their classes regularly and here you will get more knowledge and experience due to regular classes. 
• Here you will get complete support from the professors and you can clear out all your doubts easily. 
• You can also get some tips from them to crack the exams and you can also improve your communication skills. 

Hence, both of them have their own set of advantages and you can choose any one of them depending upon your interests and requirements.