just wanna know which suits best. and is it true that in writing a non fiction book, you should concentrate more on telling rather than showing regarding about the POV?(point of views) or if you cant understand me... may someone give me some advice in writing sci-fi fantasy novel?
For writing fiction, whether it's fantasy/SF or a mystery, use the POV which is best suited to tell the story. I've had stories/novels published in both 3rd person limited and 1st person POV. The method that best conveyed the story to the reader was the POV method I chose. Take a look at published novels/books similar to those you hope to write. Compare them with your writing style and objective, then select what you think will work.
Like I've been told and I've read on other threads, it's your story so do what you want with it. If you want to write it in a first person POV then go ahead and do so; if you want write it in third person, do that, because it is yYOUR story after all. There isn't a best way, it all up to how you right it. If your unsure to which you should do, then why not try writting the first chaper of your story twice - one in first person and the second in third to see which your must comfortable with.
The beauty of 1st person POV storytelling is that you can portray the world pretty much as your main character experiences it. The sights, sounds, smells, feels et cetera. 3rd Person POV on the other hand makes it easier to weave things your character doesn't experience or know directly into the story. The ultimate question you have to ask yourself is, will the story come out better in 1st or 3rd Person view? And also, in which of these POVs do you write comfortably, as the POV will not change for the length of the whole book.
Generally, I've found that I can comfortably use first person in short stories, but it gets restrictive in longer stories. In longer stories I keep wanting to have scenes my MC isn't personally experiencing, so I can't use that POV. I must use third person. I also prefer third person because I like writing in my own voice. My characters often have a different set of experiences and a different vocabulary from me, so if I write in their voices, I always feel limited in the words I can use or the things I can reference.
Because of third person's flexibility, I recommend it unless you have a specific reason for preferring first person. The main advantage of first person is you tell the story from that charcters moment-to-moment perception of events. Therefore, if the perception is changing for unchanging facts, the reader doesn't feel you were lying previously. Also, the first person POV can be self-serving for that character, if the character is presenting matters differently than you wish the reader to ultimately perceive them. First person is therefore considered an unreliable narrator. For example, you could tell the story of a cult leader, showing his rationale for the actions the reader will not agree with, but so the reader can see the leader as a person with different thought processes rather than a monster.
Do what you think will best serve your story, and what you're most comfortable with. I like first person because I can really put myself in the character's shoes. I am that character, not some dude following the character everywhere he/she goes. As for advice in writing sci-fi/fantasy novels? Simple. Go the hell nuts. Seriously, there's no (and there should be) no set rules in writing sci-fi/fantasy. As long as it makes logical sense for the story's universe, you can write about...an alien ninja boy who rides on the backs of flying space dragons. Please note that I'm not saying that this is a story you should write (or that you'd want to write). I'm not saying that at all. My point is that you should just go nuts.