The 5.75 should be the second coil in your collection. You will need it in trashy areas and it works great. It is almost as deep as the stock coil too.
The 10x12 Widescan is great for wide open clean areas, but it can be a pain to pinpoint, especially if there is more than one target under the coil. You have to pinpoint with the tip of the coil, turn 90 degrees and do it again until your pretty sure the target is under the tip. It is a pain, but I have found a lot of nice things that I missed with the 8x9 since it covers so much area and the detection field is more or less the entire coil straight down.