Choosing an appropriate tagging format

I have a lot of mp3 files which i play on my iPod and home pc via iTunes. Which tagging format, ID3v2.4 UTF-8 or ID3v2.3 UTF-16, should i use?

This forum post says that ID3v2.4 UTF-8 has problems with iTunes (read the 3rd last post). However, it was written in 2006 so i was wondering if this is still true for the latest iTunes.

Essentially I want the tagging format to have full compatibility with iTunes and iPods. Some of my music has non-english characters. I also want the format to be efficient meaning that it takes up the least amount of space for text, album art, etc.

is still the format with the best support as V2.4 has not been adopted by all players and stuff.

How about the file size of ID3v2.4 UTF-8 and ID3v2.3 UTF-16, which produces the smaller size?

Do you know if iTunes still has problems with ID3v2.4?

I do not know whether and which version of iTunes has which problems with v2.4. I only see that this forum frequently features questions about v2.4 and that the general notion is "leave it alone".
Talking about sizes: we are talking about a couple kbytes if at all. Any savings there would probably eaten up by the cluster size of your hard disc of by leaving out a duplicate track. Or by reverting to v2 which leaves out such space consuming tags like albumart.
So: stay with v2.3 utf-16 and you are fine.

I can say that I use "ID3v2.3 utf-16" for all my mp3 files and they work perfectly in ITUNES (latest verison), foobar2000, winamp, WMP, and SqueezeboxServer. I actually only use ITUNES (for portables), foobar2000 (on computer) and SqueezeboxServer (for serving my squeezeboxes at home). But again, no issues with tags.