I have or have had all of the various PW transformers. The ZW and KW fall into the "wanted one as a kid" category, so I have them but don't use them! I agree with a previous poster, I do not like the controls on the KW, and the fixed accessory voltages of 6 and 20 are hard to use. The ZW is OK I guess, but they don't thrill me the way they did on 1962! The minimum starting voltage on both the ZW and KW is too high for Williams locomotives, in my opinion.
I use a pair of 1033s, at 90 watts each they total up to just about the same as a KW. Three of them would have the same power as a ZW. I like the fact that I can set them for 0 - 11 volts for use with Williams locomotives and quickly change them to 5 - 16 for use with Lionel. I also like the 11 volt accessory supply for use with many of the vibrotor accessories, it seems just about right for the sawmill and news stand as well as being easy on lamps in lighted accessories. Of course, the 16 volt accessory output is also available should you need it.
Suit yourself, you certainly won't go wrong with either a ZW or KW. My advice is to get an inexpensive one to play with to see if you like it.
