The worth of any investment depends on a number of factors and not just the name of the developing builder alone. As far as my understanding of the Prestige Group goes they are one of the top builders ion south India and have a very good reputation for delivering good quality products.
You have not mentioned what kind of projects you are looking to invest in, whether residential or commercial. Since you have shortlisted Prestige group who have an equal market share in both segments it is unfair to comment on any one.
There was no hidden fee and all paper work was transparent. Such good work ethic is a definite plus point. As of now i do not think the prestige group has a residential real estate project in Mysore but they do have various active projects in Bangalore, Chennai, Hyderabad and Kochi.
Ever since their first successful project they have been focusing on various residential and commercial projects with equal focus and dedication. I know some people in Bangalore who have bough residential apartments by Prestige builders and they are quite happy about the quality of product offered