I was there in feb, not sure about weather at the time of year but can tell you about the place. Kerala although beautiful I wouldn't recommend for beaches. Inland is great, kochi is a great city and the houseboats are great fun. If you're with woman forget the beach there, perv locals just ruined it for me and we stayed by the pool instead. The beaches are empty but as soon as a western woman lays down men just sit around pretending they were just sitting there anyway, I was on the balcony and the girls were on their own for ten minutes and one was taking pictures on his phone, sorry but they are disgusting.
People always recommend kerala over Goa being more authentic, as I said if you want in land then yes this is true, if you want beach stick to Goa where they are more chilled and used to tourists.
North Goa is overdeveloped, you might as well be in Spain. South Goa has great beaches and is less developed, my favourite is Agonda but it is more huts, they can't build hotels which is part of the charm. Ten close by is cola beach, just off that is mini cola or something where we stayed in some tents, unfortunately the rocks in the water there make swimming a bit hard but apart from that lovely, look up cola beach tents.
Really depends on what you want, if you are happy with back to basics then south Goa is great, if you're more after the built up north the is not sure it is worth travelling that far.