Low quality MP3 encoding

Okay, so I’ve been messing around with lossless tunes lately, and when converting them from FLAC or WAV down to 320 CBR MP3, I threw a few albums through a Xilisoft converter, and just did an album with CUETools. Xilisoft took three minutes to encode 50 minutes of music. CUETools took ten to fifteen minutes. The settings were the same as far as I could see.

My question is this: is Xilisoft doing a dodgy/quick job? I’ve read an article about MP3 compression and the process seems pretty step-by-step without loopholes, not to mention that I’m encoding to CBR which takes away a few calculations on the software’s part, but the perfectionist in my head really wants to know if my Xilisoft 320s might be a little less quality than my CUETools 320s.

Check which codec both use, if they’re the same I doubt you’ll notice any difference. Maybe Xilisoft supports multiple cores and CUETools does not?

I’ve got CUETools using lame.exe (copied straight from Audacity’s native version). My question really revolves around whether there can be lower/higher quality MP3 encodes depending on the program used.

Well yes, there could be, but that’ll have to be a difference in codec.
If it’s 320 kb/s then that’s what it is, it’d be silly to write a program that encodes MP3 at 320kb/s but then not actually make any use of the 320kb/s, making the filesize unnecessarily large. So yes, technically it’s possible, but very unlikely. Any possible audible difference will be the codec.

To check for differences, you could take both mp3’s, import them in cubase, phase reverse one and see if they cancel.