I have a centerfed 220 foot dipole I am using on all bands from 160 -
10 meters. It is between 40 and 50 feet above silt soil and is fed
with W7FG open wire (600 ohm?) Currently I am using a 4:1 balun at the
output of the antenna tuner to transform impedances to an L-Network
that allows the transmitter to see a close match at 50 ohms.

I am interested in opinions on whether it would be better for me
to use a 450 or 600 ohm balun that might more closely match the
transmission line (in practice).

I believe that with the reactances involved, so theoretically it might
not make much difference. Anyone with actual actual experience
who would like to render an opinion?
Thanks,
Ed