This one's a bit difficult one. If you in search for tranquil surroundings and at the same time maybe wanna have a blast, then Goa shall be the apt place. Many might disagree with me on this, as Goa is usually associated with having a crazy nightlife with all types of bustle, but trust me, South Goa is indeed a paradise that's yet to be explored, hence it's pretty peaceful. On the other hand, Gokarna with its scenic beauty and not so happening nightlife is more like a destination where one would like to enjoy a peaceful stay.
Goa is good with too many beaches, its happening place, the beach shacks and lot of water sports activities etc. Moreover u can select either North Goa or south if you prefer less crowd. There are churches to visit, Mangeshi temple, fort etc. Select Gokarna if u want beaches with little less crowd and a relaxed holiday. The beaches are clean