oxygen sensors

[tihol_tiholov at sd27.bc.ca]

Here's what I got from a VW/Audi dealer in Vernon, BC (Can currency):
<Hi i looked into the information you requested and have some answers for
you.
1. 1988 Audi 90 Quattro, 2.3 I5
     Part number- 034-906-265-F $242.70
     We have no stock, 2-4 days lead time
2. 1999 Beetle 2.0
     In front of catalyst
     06A-906-262-Q   $40.00   stock
     Behind catalyst (could be either part number as there is a change part
way through the year)
     06A-906-265-N  $167.60 no stock 2-4 days lead time.
     06A-906-262-F  $36.82   no stock 2-4 days lead time.
 Thank you for the request
 Jim Armstrong>

So do I buy the VW upstream for 40 or go even cheaper and buy the
downstream for less?  What would be the difference, if any?

BTW, checking at a Ford dealer under 1986 T-bird 5.0 produced a $198
unavailble anywhere in Canada and the US, same year/engine in a Mustang was
$77.

Greetings,
Tihol