I have both a Z2 and C2 and like my C2 much more. Performance-wise, they're identical, so getting the Z2 will save you money (but then again, a 6P will save more money over a Z2). However, I like the appearance and finish of my C2 much more. The C2 is a bit heavier and the flat sides feel a bit more comfortable and secure to grip. I recently got an M2 head and a Detonator extender for my C2 and damn, it's a nice light!
Above the $50 range, I personally want HA. I got the Z2 because my fiance wanted a SF also and I the price I got for the Z2 wasn't that much more than a 6P, and I like the Z2's design much better, so I picked one up. I know you mentioned you want one of these SFs, but there are other very good options available such as the Wolf-Eyes 6MX or 9DX (3cell). These are type-II ano like the Z2. For the price of the C2, you can pick up a W/E M100X 4cell that blows away the C2 in output.
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