If you take my opinion
as per as my experience Goa looks too beautiful in monsoon
here are some positives it's greener in everywhere
less crowded cheaper as well you can get good accomodation in very cheap price so in cut short in monsoon
it's cheaper , it's pocket friendly, it's more greener
If you want to avoid crowds then monsoons are best. You get to enjoy beaches as well as waterfalls. But if you're a party person, then Nov to Feb is the time where you see a lot of crowds mostly Indians. Some off beat places comparitively peaceful than Goa are Gokarna, Varkala