My experience with the large coil is that it pinpoints the same as the stock, but it's also my experience that it's not quite as accurate as the stock coil using the same method. Shallow targets do seem to pinpoint much better, but the deeper ones I have to spend more time on trying to narrow it down and then more time probing for.
In most situations conventional wisdom dictates that you can cover a larger area in less time with the bigger coil, but personally I've found that you use lose the time you would have saved trying to pinpoint the target. For this reason I try to stick with the stock coil as often as practical. I save my big coil for big areas, like football or soccer fields, where 99.9% of the time I'm not the first one to have hit them with a detector and the targets aren't deep. The weight of the bigger coil can get to you after a few hours also.
I do have all three coils and wouldn't have it any other way, it's just my opinion that the stock coil is the real sweetie as far as weight, size and practicality. The other two are specialty coils, and it's up to each individual to figure out which one is going to work best in any given situation.
Steve