Hi Kenny ,
I wasn't sure which one to get for my XT-50 either but being as I like to find small gold jewelry and I had a couple of other brand detectors with small concentric coils , I thought I would go with the higher frequency coil . I read some great reviews about them on this forum also .
I have so far used the coil in very trashy turf areas and found it has great separation .
I have also used it next to the iron bars in wood chip playgrounds and have found a lot of coins I and others have missed .
I honestly don't know if I would have done better with the concentric or not but I am certainly not disappointed with the performance of this coil in the situations I have used it in so far .
I also plan on using it in streams for gold .
A lot depends on your ground conditions and what you're planning to hunt .
Your ID numbers will read higher with the smaller coil but that's pretty common , you will learn to adjust .
Maybe one of the guys who have used both will chime in and give you a better answer .
Desmond Dunne from Minelab also posted a video on this forum pertaining to both the new 6" coils check that out .
H H ,
George