You can't really compare mod_ruid2 to CL. mod_ruid2 is a patch for apache which makes sure files are being executed under its own user instead of apache. This is mainly secure, speed is not really a factor, only that for example suphp would be slower.
CloudLinux also adds security to your hosting environment, through
CageFS. But the main feature of cloudlinux, I would say, is the dividing of resources between users. Where normally one site can use all servers resources; using cloudlinux, users will be limited to only their fair share. On a side note, mod_ruid2 can also be used within CloudLinux.
Over the past weeks I've been spending some time looking into CloudLinux and I must say it looks really good.
One factor has room for improvement; MySQL. They have
MySQL Governor in beta, where you can set hard limits and if a user hits that limit, mysql will simply not be accessible for that user. This looks very similar to how apache is getting limited:
Each LVE limits amount of entry processes (Apache processes entering into LVE) to prevent single site exhausting all apache processes. If the limit is reached -- mod_hostinglimits will not be able to place apache process into LVE, and will return error code 503 (error code we selected, so that it wouldn't interfere with any other error codes). This way very heavy site would slow down and start returning 503 errors, without affecting other users.
The difference is that MySQL will be sending failures to the website, which means the website has to handle this error instead of apache returning the 503, where the visitors request won't reach the website itself.
But I think the right way to handle MySQL would be setting the limit reasonable high; and include this limit in the terms and conditions. When a customer hits that limit, apparently the website is very popular and you could offer a VPS or something. Or maybe if MySQL usage isn't really causing problems, you can just not use this feature at all.
I'm planning on using CL myself in the near future.