Lets deal with your security question first:
Mod_ruid2 is almost as secure as SuPHP. Both execute the scripts as a privledge isolated user. I give SuPHP the win by a wisker because it refuses to run files that are editable by everyone (666 and 777 perms), while mod_ruid2 will still execute this.
As long as you don't upload / setup insecure permissions mod_ruid2 is just as secure as SuPHP.
As for what I would use, that depends on a lot of factors. The better fit depends on more then just raw execution speed or security. You need to consider memory usage, the number of unique vhosts, etc.
mod_ruid2 is not compatible with a number of other apache modules and technologies that are also important from an overall performance perspective:
- mod_cache (mod_disk_cache, mod_memory_cache, etc)
- the newer apache mpms (mpm_event, mpm_worker, mpm_leader) that use threads instead of just processes.
- FastCGI and other techniques that give you the same speed advantages as mod_ruid2.
If you are going to have a lot of different sites all doing PHP, then mod_ruid2 makes sense. If its a few sites, FastCGI makes a lot more sense.