Hard to say, depends what you want. The one max is rubbish. If you're looking for a big phone you're better off going with a Samsung Note 3 (bought one myself recently, best purchase I've made in a long time). The other phones are all good. If you want a good camera go for the S5, if you want water resistance or other cheap gimmicks go for the S5, if you want a good time go with Ozman, otherwise the M8 is a great choice.
I was torn myself for a long time so I tested out the M8, Z2, S5 and the note 3. The M8 was good but the camera is horrible. The Z2 has a great camera but it is one of the most uncomfortable things I've ever held. The S5 was the best of the bunch for me but I have large hands so it felt small.
In the end I played with the note 3 and it just felt perfect. Has all the features I wanted from the S5 (except the waterproofing) in a larger package. Plus the stylus is great.