Must be your lucky day. I shipped my SE off to Minelab Thursday and my SE X1 probe is sitting on the kitchen counter with nothing to do. It's mounted to an SE upper shaft but those also fit the Explorer II.
I'll bring it along tomorrow in case you want to take it for a spin.
That said reason...
#1 Speed - I can recover a target and move on to the next much faster with the X1 probe. Less time spent chasing things around a hole or dirt pile = more time swinging the coil = more finds.
#2 Accuracy - Being one prone to multilating old silver and copper coins with my digger I now sneak up on my targets with the probe. Its rare that I put my digger into a find since buying the X1. Learning to pinpoint worth a damn also helped.
3# Iffy targets. A high percentage of my older finds are iffy signals. They can sound a lot like a rusty nail with low iron tones. When digging the worst of these one is not always rewarded with a good target but I am MUCH more likely to take a chance on these because I know I won't be wasting time chasing a nail. The X1 probe has the benefit of the Explorers tone ID so after a quick check I'm on to the next target in short order if I hear iron. Try that with any other brand probe.
4# Multiple Targets - This is not an every day event but its happened to me quite a few times. I get a decent signal, recover a coin. Sweep the hole with the big coil and hear nothing or iron. Check the hole with the X1 and the X1 says there's another coin down there! Once I dug an 1887 IH. Checked the hole with the X1 and thought it was picking up another coin or something, but it was pretty deep, X1 barely got a signal on it. Swept the hole with the stock coil, nothing but iron. Started to fill the hole in but then decided to hit it again with the X1. There's something down there dam it, I dig another 3 inche plug out of the bottom of the hole, flip it over and theres another 1887 IH with a SWEET e.g. XF/AU 1886 seated dime stuck to it!
#5 Speed 2 - Heres something I do quite often, nearly every hunt. Second to iffy targets are targets that are hiding in the shadow of nearby trash. I often think I hear a peep of a deeper coin near a more shallow trash or clad target but its too close to the shallow target to tell for sure let alone pinpoint. Again being one to mutilate finds if I'm not careful I go in with the X1 probe, get that trash or clad out of the way quick and give the area another sweep. I probably have a 70% success rate at this and theres nothing like taking home a keeper that was trying to hide. Trying to pinpoint the trash or clad with the stock coil is a pain, the deeper coin nearby pulls the pinpoint off center. Its just so much quicker with the X1 probe.
I'm completely spoiled now, I won't hunt without my X1.