LaserJet 1320 or Color LaserJet 2550L?

I'm thinking about getting a new printer and have been looking at
the LaserJet 1320 and the Color LaserJet 2550L. I haven't previously
had a colour printer before and I don't need to print colour often.
However, having the ability would be nice. I have seen the 2550L
advertised in Australia for $699 and the 1320 for $708.

I want which ever printer I buy to work in Windows (XP) and Linux
(Solaris and HPUX would also be nice). The 1320 emulates Postscript
level 2 and the 2550L emulates Postscript level 3.

According to the HP web site the 2550L comes with a 5000 page black
cartridge. I imagine the 1320 would come with a 2500 page cartridge.

According to my calculations the 2550L should work out cheaper per
page (for black only printing $837 vs $1159 for 6000 pages excluding
paper). This is based on an average coverage of 7.5% (which is
typical for me based on previous usage).

The attraction of the 1320 is that it comes with a duplexer (which
doesn't actually offer much in the way of cost savings when a ream
of paper is around $5-6), and it takes less desk space. The
attraction of the 2550L is that it looks like being cheaper to run
and can do colour as well.

One concern I have is that I know some colour printers use colour
cartridges to do grey printing. Is this only inkjets or can I expect
to be using colour toner to print grey?

Would anyone have any comments on which might be the better option
or the reliability of these printers?

Thanks.