I agree with Tristan, go for the X-1 probe, not only will it penetrate deeper than the uniprobe but it will also work with your detectors screen, meaning that it will ID things more accurately since it's sort of a 1" searchcoil. You don't have to take your headphones off to hear it, it will also work with your detectors sounds, you can use it for precise pinpointing of shallow targets in the 0"-3"+ range, you can use it for areas so tight even a 5" searchcoil couldn't go in/through. And when you're done using it you just snap it in your upper shaft and flip a switch and you're good to go using your detector.
The X-1 can also help your detector learn targets better when making a custom screen since it's also a 1" coil, and it's more precise at ID'ing targets than the, let's say 10.5" searchcoil.
The X-1 is a winner, being waterproof the probe is very versatile. The X-1 is also cheaper @ $180.
You can ask anyone here and they'll tell you the X-1 is an invaluable tool for them.
About the Pocket UniProbe, it looks to be a great probe, don't get me wrong, but the X-1 probe was made specifically for the Explorer detectors so it will adapt better to your needs while using an Explorer, now the Uniprobe can be turned into a pulse detector which is great if you're planning to do beachcombing or wading IF you live close to a lake, river or saltwater beach and you plan to hunt it/them, in the meantime I'd say you stick to the X-1.
Hope this helps.