I have both.
The bigger coil has some advantages in target identification IMO. for example with a crown cap, if you get the cap in the center of the coil it will ring high like silver. but as you move the target to the edge it will not Ding a high pitch tone, it will drop in tone. Where a silver coin even a clad dime will stay with the high pitch all the way to the edge. Also the numbers will stay in the 80's all the time, crown caps jump around as you get to the edge of the coil.
With the smaller coil it seems to me that the numbers are much more jumpy and the tones less stable. I have tried with the sensitivity reduced but it's not quite as stable for me. The bigger coil will lock on nickels and show a 50-53 number pretty darn solid. The Smaller coil seems to jump from 40-65 on a nickel.
Pin Pointing is night and day better with the smaller coil, it will center above the target 100% for me. Because of this you can separate a bad target next to a good target very well.
I believe that switching between the coils frequently is the big problem for me with the different coils. They give somewhat different readings on the same targets, and react different to differentiate between targets. Once you commit to one coil or the other and learn the way it responds that is the best way to go. It will speak to you. Switching back and forth all the time, becomes confusing in the way it responds. I definitely like the bigger coil for nickels and distinguishing crown caps. But the smaller one is way better at targeting good from bad in a complicated area with lots of undesirable rubbish the ground.