Depends on the route for me. I use my 5.8kg (12.8lbs) for hilly routes and my 8.2kg (18lbs) aero bike for flatter routes.
Taking this last weekend as an example, on Saturday I did 88km (55mi) and 652m (2139ft) on my aero bike, average 33km/h (20.5mph) and then on Sunday I did 118km (73mi) and 1413m (4635ft) on my lighter bike, average 32.3km/h (20mph). Similar average speeds but very different rides on very different bikes. Heavier, disc-braked aero vs lighter, rim-braked bike.
On the Saturday ride, the aero bike was ideal, I could have gone quicker but I was saving myself for the harder Sunday ride that included some tasty inclines. The lighter bike on Sunday was very welcome on those steeper gradients. I've done them on the aero bike and it does feel more of a chore - my fastest Strava times are on the lighter bike. Similarly, my fastest sprint times and flatter segment times are on the aero bike.
I could lose more weight myself, for sure, but at 51 I'm not as fanatical about it as I was when I was chasing my racing goals 25 years ago. Not that I'm heavy, I'm only 5kg above my 25yr old weight so now I'm at 65kg with a V02Max of 60 in my advancing years and I'm happy to allow myself the luxury of gaining incremental bike advantages now rather than focussing upon losing much more myself. That said, post-COVID when racing resumes, eventually, I will drop 1 or 2kg more to challenge for podium spots against local competition.