Better? Than what? The 10" may go deeper, but you start to lose good ID on stuff closer to the surface (according to D Johnson). The 4" isn't as deep, and takes more swings to cover an area, but utilizes the process to quickly ID in between more trash surrounding a target. The 8" is more of the best of both worlds, IMO. I am not a believer that the best stuff is deep. The advantage of deep is to find targets more shallow detectors miss. By comparison, there are many many more targets at between 0 to 8" than there are 8" and below. If you go to sites that are usually dug by others, and you like to dig dirt, by all means, go deep. If you are relic hunting in areas that had people living on it 1000 years ago, deep is good as well. But there is plenty of good targets waiting to be found that lie no more than 2" to 6" down. Part of detecting is planning the hunt. And that involves the "where" as well as the "what" (to hunt). Even the 8" concentric can find a descent sized cache at 12" deep. Just not a single coin at that depth. My F5 in AM can probably find a cache at 2 feet with the 10" concentric. My advice is to "master" the stock coil first. Learn the detector. Forget going deeper than 6-7". Let it show you how good it is at that depth first. Then move towards greater depths and bigger coils later. Above all, don't get discouraged. That is what most new detectorists do, and start trading units and trying different coils, thinking that is what makes one find good targets. My opinion.