I was lucky enough to have the mk1 and mkiii at the same time. The mkiii was the first RX100 I had but got offered the mk1 at a price that was hard turn down. The mkiii has a pop up EVF and tilty screen which although is very handy I just wasn't using them as much as I thought I would. Image quality wise I doubt you'd tell much of a difference between the two. The mkiii has a faster lens but it's also a shorter zoom. I decided to sell the mkiii, keep the mk1 and put the, almost £250 extra money, towards other things. It's not my main camera though so your preferences may be different to mine. The mk1 is still a very capable camera and I love mine.