Latest is Toastman's one, if you consider the fact that it was compiled in July, so the source code is different than TomatoUSB's one.
Apart from that, features are not the same,so it's quite difficile to compare. The naming of the different builds in all different flavors are the same, so if you want a K26 version with USB support, OpenVPN client/server you can grab either TomatoUSB Build 54 VPN version or Toastman's K26USB-1.28.7477.1…VPN version.
On TomatoUSB Donwloadpage you have also a link: http://manveru.pl/tomato/index.html
There you can find a '9055' version (so following TomatoUSB version numbers) compiled in April.
You can go from one to another by 'Updating' so it's not a problem, just try one and change if you want.