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Most guys recommend starting with a 5/8.
Smaller blades have great manoeverability, but are hard to judge the angle correctly if you're inexperienced. They're also more awkward to learn to strop...

Sounds like it's largely down to personal choice on them really. they'll all give a great shave. With one exception they all need honing, so you have to weigh the cost of that in.
They're all carbon...