I prefer not to download songs from iTunes because A) the quality is 256 and I prefer 320 and B) they only let you play them on authorized devices. I'd much rather get a cheap used CD on Amazon and burn the tracks.
A1) Judging quality purely on bitrate without accounting for compression format isn't accurate (and technically, judging 'quality' based only on bitrate when talking about a single format is only of worth when assuming the source was close to master and therefore not affected by generational decay). iTunes doesn't use MP3¹, it uses AAC². AAC is a superior format to MP3
by technical virtue alone (and it also helps that Apple's implementation is basically tied for - or in - first place in the tests judging comparative quality amongst AAC encoding software).
¹MPEG-1 Audio Layer 3, originally introduced in 1991
²Advanced Audio Coding, originally introduced in 1997 as MPEG-2 Part 7, or in 1999 as MPEG-4 Part 3 with some minor changes. The MPEG-4 form is the one that everything uses.
A2) The issue is something called transparency, which is the point where the encoded file is audibly indistinguishable from the original source. When encoded with a high quality encoder (i.e., LAME), MP3 reaches transparency anywhere between ~160kbps and ~224kbps, depending on content. AAC reaches it between ~128kbps and ~192kbps, again depending on content and the encoder used.
B) That's not true at all. It
was true back before iTunes Plus was introduced in 2007, but that was the whole point behind why iTunes Plus happened: higher bitrate (the DRM-encrusted files they used to sell were 128kbps, not 256kbps), and no DRM. The files can be played anywhere, so long as the player supports AAC. Apple switched the entire Music Store to the Plus format in April 2009. Music Videos were switched over to the Plus format some time after that. The only things that iTunes sells that are restricted by DRM are the TV Shows, Movies, Audiobooks, Books, and probably the Apps (although it wouldn't really matter since you'd have to have an iDevice for them anyway).