I own both the S.E.F. 6X8 and the Sun Ray X 5.5 that I use with my E-Trac. I just recently purchased the S.E.F.6X8 and have only used it one time. It seems to work fine in trashy areas and covers more area then the Sun Ray X 5.5.
I have owned and used the Sun Ray X 5.5 for some time and used it many times this past fall. It's a great trash buster, the thicker the trash the better it performs. I have pulled many silver coins out of stacks of nails and aluminum trash. It gets really good depth, and pin points right on the nose.The only complaint is the depth indicator is not very accurate. It has a tendency to show the object to be shallower then it is. Haven't found that to be a big problem.
Another useful item you will find about the smaller coils is the ability to work closer to steel or iron posts. The standard 11" coil that comes with the E-Trac can be a problem in that area. Ether of these coils are much better.
Hope this helps.
Rick IL