You will lose not only the charge wizard button as tpi said, but also the indicator light that tells you which mode your charger is in. Those may or may not be important to you.
There are instructions at bestconverter.com to show you how to modify a
9100 series pendent to provide those services, but it would seem easier to me, as well as cheaper since you don't have to buy a pendant, to just install the 12v board.
Also, on a related note: the new board only has a single 12v hot lug coming from the converter. Some of the old 12v boards had 2 of the hot lugs. If you keep the old board and it has two of the 12v hot lugs, you will have to jumper between them.
