Ranker X is expensive, and the UI sucks. I’m not a big fan of Ranker X.
Money Robot doesn’t give you full control since it’s mainly targeted at SEO newbies, so it’s not very versatile. Also, it has zero cost on backlinks because they own their own network. So when users submit with Money Robot, they don’t need captchas or have to deal with captchas, root domains, Google indexing, etc. Users can build permanent do-follow links.
That being said, it leaves huge footprints, while Ranker X is mostly for advanced users and doesn’t leave many footprints. You can use Money Robot once or twice in a project, but after that, if you keep using it on the same project, you’ll be repeating the same referring domains, and the SEO value/signaling will be lower. Not zero, but lower.
I would personally use Money Robot once, or maximum twice, at a time. On the other hand, Ranker X and GSA SER use generic platforms, so they’re much safer, but the links are not long-lasting. My best pick is GSA Search Engine Ranker for all tiers, especially if you need constant link building.
You’re right that if tier 1 breaks, it loses the link pyramid and breaks down. That’s why we need to create T1/buffer sites very carefully, then point Ranker X or GSA SER to the later tiers. Still, if you’re smart enough, you can manage T1 with GSA SER or Ranker X.
If you’re ready to spend some time, at least a month, reading a lot of internet guides and doing experiments, I would highly recommend buying the legendary GSA Search Engine Ranker. I call it legendary because you have full control over what you’re going to feed, how you’re going to feed it, etc. There are also a lot of add-ons, from premium high-quality custom site lists to custom engines, and it supports almost every third-party API on the planet.