If you have no other reasons for your choice, you could go AAC, which I'm sure iTunes handle perfectly gapless when needed.
In general, AAC is smaller than MP3 for similar quality, so your reason for not using MP3 isn't a valid one.Also, you can save loads of space for no noticeable degradation in quality by using VBR instead of CBR.
Serves me right for typing while watching the Champion's League Final!
The settings used in XLD aren't going to matter for iTunes playback. iTunes will not be able to automatically determine if a song is gapless or not. It will however take the time to scan each track after you add them to your iTunes library for gapless playback. The settings in XLD are mainly irrelevant for this purpose as iTunes dictates how the songs will be played back without gaps, not the songs themselves. I wasn't even aware that XLD offered gapless encoding settings for Lame (or anything else) yet I have been using it for a solid year now ripping to ALAC and Lame mp3 and iTunes has not had any gapless issues.
Unless XLD is doing something out of the ordinary, there is no need to configure it to do anythig about gapless playback when encoding mp3 using Lame. I can't speak to other encoders and formats, but considering the topic is about mp3 (not aac) and Lame is most likely the mp3 encoder used...Regarding tracks that contain silence at the end (or beginning) versus tracks that do not, there is no reason to entertain the idea that they should be treated differently.
I was simply pointing out the age of the news updates and that XLD has made some changes since.
YMMV and any personal experiences in these forums (mine or yours) should not be taken as cold, hard fact.
There is no settings in XLD to enable or disable gapless.