I'm kind confuse about it, can some one give me a hand with this...
- Which one is better.
- Which one do you use and why?
- Personal Opinion and advise.
It's difficult to tell what is being asked here. This question is ambiguous, vague, incomplete, overly broad, or rhetorical and cannot be reasonably answered in its current form. For help clarifying this question so that it can be reopened, see the FAQ.
RAID is a storage level function. You can use the various types of RAID apart from any RDBMS. RAID controllers are integrated with consumer-level products these days, so it's common even for home PCs to use it.
Replication in RDBMS terms is a mechanism for taking data from one place, and putting it somewhere else. Some flavors of replication allow for merging data that originates in more than one place.
You can go into quite a bit of depth on either subject, but they are very different things.