I'm really looking for which one is more user friendly, updated more frequently (possibly from suggestions or requests by users) and has most available encoding options...
I must admit I don't use either, but I think the response you will normally get will be users recommending the one they use - i.e.: subjective rather than objective.
I think both are pretty evenly matched, and it probably boils down more to what you specific requirements are - which you haven't stated.
As far as downsides: WACK requires the .NET framework (no biggie), and MAREO only works with tracks I believe.
One question that I do have about AAC encoding using ITunesEncode is: It encodes using the encoder available in your current version of Itunes, right? So the Itunes AAC files that received such high ratings in the new 128kbps ABX test results would be available to me using that specific version of Itunes.
I believe I am right in saying that it will encode using the settings you have chosen in iTunes (e.g.: 192 VBR M4A over 128 CBR M4A) but you can specify the actual encoder on the command line, using the -e switch.
-e EncoderName Lets you specify the encoder iTunes will use.
Choose from "AAC Encoder", "WAV Encoder",
"MP3 Encoder", "AIFF Encoder",
or "Lossless Encoder".
(Default is "AAC Encoder".)
I think then that the answer to your question is "Yes" - as long as you have set 128Kbps VBR M4A as your codec of choice in iTunes then when using the "AAC Encoder" profile you will get 128Kbps VBR M4A, rather than the default 128Kbps CBR M4A files.