You'll get more fruit flavour by adding to secondary, but you'll get a different flavour from adding to primary, more wine-like. Fresh fruit doesn't taste like fermented fruit. Fruit added to primary tastes fermented, while fruit added to secondary tastes more like fresh fruit. I've added fruit to both primary and secondary/tertiary in the same batch to get more depth of flavour from the fruit. It just depends on what you're trying to get from the fruit. Regards, GF.