Depends. If you have a like minded friends group, you can go with friends. If your partner shares similar interests like you, then go with partner. If you don't find like minded individuals but want to travel/discover yourself, go solo.
Each has its own dimensions. solo of you're looking to grow as a person but it must be for a longer period of time, a month minimum is good. Solo traveling helps you meet people and explore destinations that one may not otherwise for the risks that it may entail - I will say that every person should solo esp on coming of age and for long period of time preferably in different culture and geography which is to say a different country but in India there are so much diversity of culture that one could go to a different done, be like a South Indian to North East India or north India and while feeling at home experience different cultures. Solo travel helps one grow as one learns how to cope and learns humility by experiencing the richness if human cultures. Couple - for exploring while having fun with your friend or partner. Group traveling- entirely for fun and good times, for memories to be shared ... my views only - thanks
The pros of travelling in a group with a tour guide: The tour guides have more local knowledge than we do. They know local customs and cultures. They can teach us all of these during travelling. As well as this, They can speak local language. This means that they can act as a translator in communicating with local people especially when we buy things or have meals in restaurants. The cons of travelling in a group with a tour guide: travelling in a group is not flexible. We are not able to control over our arrival and departure time. We cannot spend as much or as little time as we want at any given places because we have to follow the group schedule all the time. As well as this, if we travel alone, we can sleep or eat when we please.
Every place has its own charm.. like I would like to go to a place like Europe alone, so as to patiently explore the museums at my own pace.
whereas places like Maldives, Kerala, Sri lanka with my partner, as it gives a very romantic vibe
And places like Australia, South Africa, Goa.. in a group would be more fun.. But that does not make it a categorical point for me.. I went to Australia on my honeymoon and thoroughly loved it.