Up and down appear similar. Not saying it's the same for everyone.
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Cable internet, ie DOCSIS, tends to be provisioned Async to better meet consumer demands. Cable internet tends to be oversubscribed like most consumer internet technologies.
DOCSIS 3.1 supports speeds up to 10Gbit down and 1-2Gbit up, and DOCSIS 4.0 supports speeds up to 10Gbit down and 6Gbit up. Many DOCSIS 3.1 and 4.0 cable modems have Ethernet port speeds of 2.5Gbit or 5Gbit, some as high as 10Gbit.
Fiber residential internet tends to use PON or passive optical networking.
GPON is normally 2.5Gbit down and 1.25Gbit up, and there can be anywhere from 1-128 customers on a port, sharing that bandwidth. The customer premises equipment, aka ONT for GPON tend to be provisioned with 1Gig up and down, or less, most GPON ONTs don't have Ethernet side port speeds over 1Gbit.
XGS-PON is normally 10Gbit down and 10Gbit up, and there can be anywhere from 1-128 customers on a port, sharing that bandwidth. The customer premises equipment, aka ONT for XGS-PON tend to be provisioned with up to 5Gig up and down, or less, most XGS-PON ONTs can have 1, 5 or even 10Gig ethernet ports.
Fiber providers tend to try and make them selves look "better" than Cable by offering symmetric speeds. Cable providers could offer it, but it does not take advantage of their available spectrum on the coax for what their customers want, so they market more on download speeds...
That being said, most cable providers offer horrible upload, especially on residential. My small business cable is 100 down, 20 up, and I don't feel like upgrading as to get any increase in up, I need to move all the way to 300 down, 30 up, and that would over double my bill. Personally 20Mbit up is my minimum threshold. 100Mbit down residential service is either 5 or 10Mbit up from Cox.
The bandwidth realities is that the average bandwidth consumption of consumers does not go up much with even a 10x of the download speed, once a decent minimum is hit (like 100Mbit). But many consumers are willing to shell out $ for "faster"
-Harry