For my money I would go with a ZW transformer. They are easy to work on and also will boost the voltage when using the whistle control. You can't beat them for operating post war equipment. If you are going to use the occasional newer locomotive I would add separate horn and bell controls as they seem to work better with the newer equipment and you also get the proper DC offset. Also as previously pointed out TVS's should be added as well. They are dirt cheap and provide protection for the new electronics.
My 2 cents