In terms of continuous playback, would an MP3 post-process using gapkiller on split MP3's be a better solution than ripping to a large MP3 then splitting using Musicutter ?
First, keep in mind that Gapkiller actually has both functions in it now: The hand-trimming feature is there, as well as the "split a large MP3" feature. So Musicutter isn't the specific issue, it's the method.
As I
state in the FAQ, the hand-trimming with Gapkiller produces slightly better results than simply splitting a large MP3. However, it takes a lot of work to get it right, and you MUST configure WinAmp properly ahead of time (installing the referenced plug-in) to do the trial-and-error previewing.
I am not sure if the wav splitting process itself intoduces a gap as part of its processing,
Unlikely. The encoder is what's adding the gap. As I
state in the FAQ, the encoder adds the silence to the MP3 files itself.