Hmm you have me concerned now. The main selling point that the sales guy had over the Xerox V180 was that the c3070 is vacuum fed, but he had always said it was the 2 tray feeder (can't remember why he didn't recommend the 3 tray one...is it significantly more?). I will be really p****d if he's lumbered me with the friction fed after all that.
Edit: I've just had a look at the specs of the PF-602m and it looks like the PF-602m is an air assisted feeder, where the PF-707 is an air suction feeder. Is there much difference in performance?
Both the PF-602 and the PF-707 have air assist; but the PF-602 has ribbed rollers the pull the top sheet into the paper path, whereas the PF-707 has a vacuum behind a perforated belt that moves the top sheet into the paper path.
The C3070 is spec'ed for up to 350gsm paper weight, but only with the PF-707, and in all three trays. With the PF-602, the spec is up to 300gsm, and only in the lower tray (the upper tray is up to 256gsm). That means you will not get the benefit of automatic tray switching with 100# cover stock (271gsm) with the PF-602 for longer runs.
You'll have more flexibility keeping more different kinds of stock on line with 3 trays in the PFU instead of 2.
The PF-602 has a total capacity of 6,000 sheets (based on 20# bond/50# offset); the PF-707, up to 4,630 sheets, because of the space the vacuum mechanisms take up. Besides lesser cost, higher capacity may be the only advantage of the PF-602.
Both PFU's are spec'ed for coated sheets in all trays.
Depending on how your vendor structured price, the uptick from the PF-602 to the PF-707 varies. While the cost differential between the two PFUs, taken alone, is not slight, the differential in the total cost of the C3070 will be incremental -- especially in terms of a monthly payment.
The choice to opt for a PF-602 instead of a PF-707 is almost always budget-driven; and if budget is a real constraint, there are other options (e.g., the LU-202 or the LU-202XL, which offers banner sheet feeding). From a functionality standpoint, the PF-707 offers you more, and again, it's the only choice that gets you 350gsm weight -- better for business cards.
Honestly, I don't remember when's the last time I sold a PF-602. For a bit more of an investment, you can have significantly more functionality with a PF-707. In my opinion, the choice of a PF-602 is a false economy.
The more you run coated and cover-weight stocks, the more you'll appreciate the PF-707.