The battery usage is the same no matter what coil is used.
As far as the performance, I've never had any trouble here.
It's exactly the same as the stock coil, just bigger.
Being as it's bigger, you do need to be careful when pinpointing
as any error due to sloppiness is larger due to it's size.
But I've never had any trouble, and am about as accurate with it
as I am the stock coil.
Also, being bigger, it's a bit more prone to falsing as it's a bigger
"antenna". On the plus side, it goes 2-3 inches deeper than the
stock coil. I've found to reach it's full depth potential, you need
to run it fairly hot, which can also increase falsing.
But I don't recommend doing that until you are used to it and
can tell a false from a real repeating signal.
Myself, I choose the coil to match the area I'm hunting. If it's a large
area, and not overly trash cluttered, I use the 9x12.
But if I have less room to swing like in dense brush, I'll often use the
stock coil.
If there is lots of trash, or the swing room is really tight, I'll usually
use the sniper.
When using the 9x12 and pinpointing, the side to side measuring
is pretty critical. So I always keep checking side to side all the way
to the tone cut out point when pulling back.
With both the stock coil, and the 9x12, that side to side tone area
is the same shape as the coil. It narrows up when you near cutoff
as that is the way the coil is shaped. And that is the most critical
area when you near that narrower point before cutout. If you are
off there, the error can be sizable being as the coil is large.
That's why it seem less accurate to you. But in reality, it's just as
about as accurate as the stock coil as long as you are careful.
