If you are like me, you have tons of archives lying around in different formats (zip, tar, rar, tgz, tar.bz2 etc). In cleaning up my stuff, I have decided to basically leave my archives alone ( and generally access contents via archivemount or avfs ). As a brief aside, for the most part I will not be writing to these archives, but on occasion I or an application may be write configuration files/index files/description files/stray files ... to these archives.
However, I would like to have a preferred format that I convert these archives to when I clean up an archive. Some factors for this archive format are clear: it should be easy to convert other formats to this format, preferably directly; accessing files in the archive should not have significant overhead, size is of some consideration but not major, as long as an archive is not twice as big as the same files when extracted.
Now I am not so naive as to expect people to reply with "the best archive format is ...", rather I hope to get some ideas of the pros and cons oif various archive formats that you might use in this situation.