I've visited both, trinity college is fantastic and is a sister school to Cambridge university, steeped in history (as is King's) founded in the 1500's with a very admiral alumni - Oscar Wilde, Samuel Beckett, Edmund Burke, W.B Yeats and even Hozier! additionally Dublin is an exceptionally beautiful city and personally it is my favourite!
Kings however is similarly very prestigious and the city of London has much to offer, the prices of living in London may be substantially more expensive but you are getting your money's worth through a world-class education! alumni include Thomas Hardy, Alan Rickman, John keats!