Replacing O2 sensors

[Pewe]

When searching for details of O2 sensors (GS300 ) most appear to come wth the plugs, use of which requires removal of items from the passenger compartment.

I have, however seen some lambda sensors which come not with plugs, but with bare end wire and four plastic coated cable joiners implying that they should be fitted by joining cable.

So would anyone care to comment on why the cable joining method should not be used on the O2 sensors on the Lexus, as this does have a major impact on the time to fit, and therefore the labour costs of fitting, replacements.