Need Oxygen Sensor...but which one?

Can anyboy help here?
I have a 91 Honda Accord. Looks like I need to replace the Oxygen Sensor.

Looking to spend as little on this car as possible, but want the o2 sensor i put in to not fail 10 days later either.

this site (see link below) has 3 different sensors....does it matter? should i just go with cheapest?

http://www2.hondiscountparts.com/parts/parts1/hondiscountparts/wizard.jsp?year=1991&make=HO&model=ACC-EX2-001&category=C&&part=Oxygen+Sensor

Thanks!

Same problem here. I bought the Bosch. Anyone know how to put it on?