Read this thread and then you decide.
Go with which ever is easiest for you.
MY battery is grounded out on the tongue and
at the power center.
I wanted to put the disconnect switch near the power center and my
positive wire runs from the batteries on the tongue to the power center
with no tap offs in between.
Some trailer take power from the battery and split and some goes to
the power center and some goes to say a slide out motor.
In my case I could disconnect the positive wire at the fuse block in the
power center and everything in my trailer was off line.
I put the switch in the toe kick area next to my power center in the
Most switches are going to be found in the positive wire and the switched
devices will be grounded on the negative wire.
Read this thread for an active discussion. Some folks are passionate about
which wire they think the main switch should be located in but in fact
either side will get the job done as long as there is nothing up stream from
the switch except the battery(s).
AND I totally agree with you. Battery disconnect switches should be
standard equipment on all RVs. I've had to install my own on all 3 of my
trailers. I expect to have to add one on my next trailer if there is a
Good luck and happy camping!