Brand is better. Most agencies in India are unprofessional and chaotic. Upstarts from big agencies eventually quit to start their own thing, usually fail within 5-10 years. Mostly have creative flair or professional experience but not enough business sense or financial know how to run an agency successfully.
I've worked on both sides and although agencies have a wide variety of work incoming, the quality is generally sad. Very few brands in India pushing the envelope too. All things considered, easier to work on brand side plus more growth potential imo for good brands. Agencies are hit and miss.