No expert but I do wonder how a cheap client can be more secure than a professionally managed server.
If you mean robustness against brute force volumetric and resource exhaustion attacks then yes large systems are going to be more resilient than small systems for the same reason a big boat is harder to swamp with waves than a small one. The whole business model of things like Cloudflare is to put your site behind a gigantic CDN that is just so damn big it can weather volumetric attacks. It's a brute force solution to a brute force problem.
In this case I was talking about more intelligent distributed attacks against distributed protocols. Those types of attacks are very hard to protect against in general.
Most systems deal with it by being closed and isolated or at least having fairly strict policies about who is allowed to participate (e.g. BGP). In an open P2P network you're going to have to figure out a way to permit resiliency in aggregate without a trust model, which is IMHO an unsolved open problem in protocol design. There's been some progress in countermeasures but no huge breakthroughs.