Powerline sucks. It's slow (in most houses you're lucky to get 100mbps throughput even with high end "2000mbps" adapters), and it tends to suffer from bad jitter and latency spikes to the point where it's more like bad wifi, while MOCA is generally pretty close to ethernet in terms of having basically no additional jitter or ping spikes (only real downside is the cost of the MOCA adapters, and that it's a shared link between all the adapters so you're limited to eg. 2.5Gbps combined on all MOCA links, which isn't a problem for most people).
Also, for the cost of either powerline or MOCA adapters you can buy a big roll of CAT6 CMR and a fish bit and run ethernet through the walls (just do a good job on the patches if you're renting).
I have to begrudgingly agree with you. A couple years ago I plopped a couple powerline adapters on either end of my house. They're on different circuits, but the same phase of the panel.
It worked great. I got a consistent 80Mbps through them. I was happy and probably commented here or elsewhere about how they can work, or, "don't dismiss it, it might just be the trick."
Well, now they're pretty flaky. They still work just enough for me to keep using them, but other WiFi issues I'm having are convincing me that I gotta stop being lazy and run some cable to all my rooms. (I even have a crawlspace! It will be relatively easy if I can just get cracking on it.)
I don't know what changed between then and now. Phone chargers on the circuit? That random smart plug I bought last year? My A/C cycling in the summer? Doesn't matter. Powerlines are a hostile environment for high-speed data.
If you have accessible spaces and don't have high ceilings, this is true. If you have neither basement nor attic (or they are not accessible easily), or you have ceilings high enough to require crossbraces, and especially if you only need to make one or two runs, MoCA is very cost-effective.
I've gotten a pretty reliable 400-500mbps over a "2gbps" powerline adapter. Granted this was in small 1-2br apartments, but you're probably dealing with only one coax jack in the whole place and it's not feasible/worth it to run your own cabling.
Imo, in a small 1-2br apartment it's easy enough to run ethernet and hide it along the walls, either by tucking it under the moulding if you have carpet, or using cable hiders.
I'm also just laser focused on good consistent latency though after years of suffering awful cable internet and trying to minimize all latency that I could control (https://i.imgur.com/i84mIsD.png was what it was like during the day in 2020 in the first wfh period. Luckily I've only been getting consistent spikes up to ~200ms throughout 2021 /s).
edit: That ping was on hardwired ethernet with no load as well, and Rogers (realistically the only ISP where I live in Canada because my available Bell DSL connection is too slow) was throttling uploads to 4mbps.
My go-to solution for routing ethernet while renting are 3M Command Hooks. They are remarkably strong, while being easy to remove – albeit a tad bit on the expensive side.
Also, for the cost of either powerline or MOCA adapters you can buy a big roll of CAT6 CMR and a fish bit and run ethernet through the walls (just do a good job on the patches if you're renting).