The whole idea of what gralat farming is the best one is a hard one, of course with each of them, they have their negatives.
While pyrat quest gets 1000 gralats in about 10 minutes, you'll have to deal with numerous players, and you can only do it once a day.
Looting is fairly easy to get loot from, and you wont have to battle oth players, but it is very time consuming if you want to sell loot for the highest prices.
Farming can take time and can get boring after awhile, but you could be getting 3000-4000 in a few hours with this technique.
Bug catching can be hard, as much of the time will be spent battling other players for one bug. If you want money from it, build up more bugs before selling. Also bug catching is not possible in the winter and bugs vary on the season.