It comes down to personal preference.
I like the pistol grip head for when I'll be doing static viewing, like at the range. Just set it and leave it. If you will be doing sweeping motions such as when glassing, you may prefer the fluid head to smoothly pan from side to side or up/down.
Really the only way to know for you is to try both styles out. Each have their place. I have the Manfrotto 128RC fluid head and a 322RC pistol ball type head. Really like them both for their repsective purposes. Both have the q/d shoe.
Have the Manfrotto 190XB legs and a window mount which covers my uses nicely.
If you are only going to be glassing with binos, and not with a heavier / longer scope, you may like the pistol grip head. The size of most bino's will keep the weight low and centered mostly over the head. The grip can also be moved to the left or right side, where as a fluid head usually has a handle the comes out the back and angled down slightly. Depending on your setup, this handle could get in your way.
The best solution, although a little more costly is to get both. I did just that so that I can have a head mounted to my legs and window mount at the same time, which makes swtiching my Razor spotting scope just a matter of slipping it out of one and right into another with a quick click.
Edited by FireEMT5 - March/11/2011 at 11:23