I have had the 8 x 6 SEF, the 8 inch minelab and the Sun Ray X-5 stealth coil. Additionally, I had the joey. If you are looking for a smaller coil, without question, I would get the stealth X-5 asap. Next, I would choose the joey coil.
The X-5 works well in heavy iron conditions, gives good depth for it's size and beyond that, it is superior on scraped lots and playgrounds, as it allows you to get close to adjacent targets.
The Joey is often overlooked as a goto coil, but I have used it on scraped lots as well as heavy iron infestations.
Finally, my 3rd pick of the four cited would by the 8x6 SEF. The footprint is wider than the joey and the X-5, but it gives great depth.
The Minelab 8 inch is just too close to the stock coil for my tastes. I just was not impressed as much as the other coils.
Anyway, good luck to you with whichever decision you choose.
Be grateful that you are not like me, and just bought the CTX 3030 and all coils with it. LOL I was going to hold on to all those other coils and my EX II and Etrac, but alas, I have decided to sell those and might get another machine. I have only 16 hours on my CTX and it is feeding a lot of information to me that I don't have down yet and I am truly impressed with it regardless. I am learning, just as I did enroute to having all those other coils I am getting rid of.....LOL
HH
Dennis