[i.h]

You're always going to have a difference in latency. Mainly down to ISPs core networks and the numbers of hops it takes to your home gateway. This applies even with multicast and CDNs.

as someone who works for an ISP that you will have heard of:

not enough of a difference to matter with any ISP worth using, though - and even the very worst connection is still going to have sub 1-second latency to a CDN server, so any excessive streaming or video call delays are not due to that.

the differences are not really due to the core network, but instead in the access side. This is especially true for anyone who doesn't have fibre to the home as both DOCSIS and DSL can introduce various delays and jitters depending on local conditions, and all bets are off with 4G/5G

we also find that even if we produced the most perfect internet connection ever created, people are still going to ruin it by using wifi or homeplugs or other low speed high(er) latency connections. COVID was a huge case in point, as people would insist on using wifi for their important video calls, even the ones that end up on TV, and then moan because it drops out. MPs were a particular example, even though Parliament gave them a WFH equipment budget and (IIRC) issued advice to run ethernet cables.