I have both, plus the pan attachment. The pan attachment lets you leave the pistol grip locked and still move side to side. It's nice for grid glassing with the pistol grip head, and also when using the rifle rest attachment without a head.
Both heads have their place.
The pistol grip head I love with my 15x binos especially. I was just using them before coming in tonight on my window mount with the pistol grip head checking out some whitetail. We got a cool evening so they were in the alfalfa. If you don't do a great deal of grid glassing the pistol grip head is really nice. I like that I can scan quickly with it just by holding the trigger down, check all the likely spots quickly. I can really get dialed in on a deer fast with the binos and this head also. It still works fine with the spotter too, I had my STM 65 on it tonight to zoom in on the furthest buck. It seems a little more awkward to get dialed in on a critter with the pistol grip and spotter than with a regular head, but it's not bad at all just takes practice.
The pan head is also a little different than most as it uses 2 separate levers for adjustment, not the one like most heads. It locks really steady and is very smooth. It's nicer for grid glassing. If I planned on using the spotter 80% of the time and the binos 20% it would definitely be my pick of the two. I seem to use them more 50/50 and prefer the pistol grip head a lot of the time.
One of the biggest things I like about the pistol grip head is using it with the rifle rest attachment. It's sure faster to get locked on target with it for me than the pan head that needs the 2 separate levers to lock it. With the pistol grip head I can just hold the trigger until everything is perfect and then release it for the shot. I just have to be careful to keep the rifle supported so it doesn't tilt sideways when the pistol grip trigger back, that can happen if you aren't careful. The pistol grip head has a groove for using it as a rest with it laid sideways also for times when the rifle rest attachment isn't with you or you need it fast.
I really like their quick attach system so I can use my optics with my window mount or either tripod without a lot of switching stuff around. I have the compact medium tripod I really like for times I don't need to stand, and a Promaster 525T with an Outdoorsmans adapter for times I need extra height.
Hope some of this helps.