Well you know I like mine so I won't go into the merits of the ballhead. I've had mine a year now and I'm as happy with it as the day it arrived; the best ballhead I've used.
I don't remember the exact details, but when I was doing my research last year the prevailing sentiment was for the single pan version, as the double pan didn't do a particularly good job as it still needed an additional RRS or Novoflex piece to do serious stitched pans. The second pan head is built into the clamp and has limited usefulness.
I use a panoramic 617 film camera (the negative is three 6x6x6cm long)
so I have no need for the DP version and I bought the SP version, which I recommend to you. I'll link to the one I bought below. If you buy the DP version you have to buy the Arca-Swiss clamp, if you buy the SP version you don't.
Your choice of the SP version
includes the A-S clamp. Take a look at the clamp, that's a double-decker clamp with the regular Arca-Swiss jaws that we all use on top and a proprietary jaw for a new rail system on the bottom. This design has caused concern for many users as the safety stops on regular A-S camera plates can no longer stop a camera sliding out of the clamp as the jaws are raised above the top surface of the clamp.
I bought this version of the SP Z1
and I recommend it because you won't have to deal with the weird A-S clamp. You can buy either a lever release or a screw knob clamp from Kirk, RRS or Wimberley; all are good. I have a fetish about Markins screw knob clamps so I got one machined to fit on the Z1 ball stem; it was an expensive custom job that I don't particularly recommend to others but I have several different brands of ballhead and they all have the same Markins clamp on them. Pic below shows the Z1 after I put the Markins clamp on it.
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