just a quick look at the components and specs looks like the f85 is a better bang for the buck. They're essentially the same bike...650c, al frame, carbon fork, ultegra rear 105 front...
that said, the f85 has a more aggressive geometry. The z70 looks to be more of a comfort bike. If you're going to be doing long, relaxed rides, go with the z70. If you don't mind the more aggressive position, f85.
If you really want to know which one to get though, you have to ride them. The best "bang for the buck" is going to be the one that fits you the best.
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