Does anyone have a quick summary of the difference between the 2820IPPBX and the 'V' models?

http://www.draytek.co.uk/products/comparison.html implies that the IPPBX is the only one with an FXO port, but the manuals for the 'V' models show that they can happily route calls out over PSTN, so surely that's the same thing as having an FXO port?

From reading the different manuals the only major difference I could find was that the IPPBX model has call attendant and voicemail. Are there any other differences?

Thanks in advance.