Mike,
I purchased the Excelerator 12" coil. It seems to me to be lighter than the 10.5 stock coil, but I haven't actually weighed it. Some here have indicated they think the Explorer is not balanced very well and is somewhat heavy. I also own a Troy Shadow X-5, which is the lightest detector I've ever used, but since I cut my teeth on the old Garrett Master Hunter ADS series, I don't find the SE to be heavy at all. I think a lot of the weight perception is how people swing the coil, how long they extend their detector shaft, and their speed. Also, swinging from the elbow instead of your shoulder...stiff arm style...can take its toll.
I've always been a slow, methodical searcher, and have never 'hurried' to get done with a site. I shift my weight from foot to foot as I pass the coil in a straight line in front of me. I wait to complete the pass before I go the other direction (in other words, no quick choppy swings). Bottom line, operating technique can affect your perception (and endurance) when making passes with any detector, especially with a larger coil.
As to depth, I have only used it several times, as I haven't been able to get out much this month, but my impression is that it is a very deep seeking coil! Strong signals at 6 and 7" tell me that I could have easily detected targets twice that deep and have them register with no problem. Fact is, I can count the number of coin targets I've recovered 10" and deeper on two hands, and that's in over 30 years of detecting, but with many different detector models. I have confidence in the Excelator coil to find such targets, but so far, I haven't walked over any that I know of....they're out there, though.
(Heh, what's more frustrating than getting a deep deep target and knowing that you better not dig it for fear of the park dept, or homeowner etc. seeing you put your arm elbow deep in a hole that you dug in their lawn?...sometimes I have to pass on them just for the image of the hobby).
I think the advantage of the large coils is two-fold...ground coverage and depth. The 12" coil also has no problem pinpointing shallow or surface targets for me, and I believe (from the sites I've hunted so far...) that target separation is still exceptional. It used to be that with the old, heavy concentric 12" coils, using them to try to find deep targets in moderately trashy areas was counter productive. The cone shaped field simply took in too many targets at once from the soil matrix. The double D coils are a different animal. The shape of the field is such that one CAN differentiate good targets in a trashy matrix much better. I plan to use that coil in open areas to cover more ground and for heavily hunted areas that still might have a carpet of coins one to several inches below the maximum depth other detector/coil combinations can reach.
I've seen enough testimonials for either brand of coil, from people whom I respect on this forum as expert hunters. I think you'll do well with either of them, if you use them in the right areas and adapt your hunting techniques.
Knipper