Knee warmers surely can negate 3/4 bibs.
And 3/4 bibs can negate knee warmers.
If conditions are changeable and you might want to remove them then knee warmers make sense. If you're going to be keeping them on for the whole ride, knee warmers and bib shorts offer no advantages over 3/4s and some downsides.
Less kit is the main one, but I confess more kit is the itch.
@snoops started
London Fixed Gear and Single-Speed is a community of predominantly fixed gear and single-speed cyclists in and around London, UK.
This site is supported almost exclusively by donations. Please consider donating a small amount regularly.
And 3/4 bibs can negate knee warmers.
If conditions are changeable and you might want to remove them then knee warmers make sense. If you're going to be keeping them on for the whole ride, knee warmers and bib shorts offer no advantages over 3/4s and some downsides.