cactus----
A generic answer to that would not be fair or accurate.
An rpm compiled to install a one-off or specialist type of facility is the easiest/preferred way - yes, I would generally agree. However it does tie you to that contribution, its author and his or her continued ability or generosity for updates. A good example of that is the wonderful Jesper's ClamAV contrib for SME6.
Putting WordPress down in the 'core' (as opposed to an easily maintained iBay) may lead to difficulties implementing regular or security updates from WordPress. ie these are base files and not wrapped up in an all-encompassing rpm. By not having such an immediate update facility reliably available, or expected to be available, you leave yourself vulnerable when there is a security alert. Putting this another way, the WordPress people are not necessarily going to be able to help you with SME difficulties and there may not be any SME people able/willing to help with a user-application such as WordPress. Just my opinion;~)
----best wishes, Robert