Scans_Daily

Personally, wether they retain it or not, what I care most of all is one thing: Consistency. If you retain the honorifics, you keep the honorifics whenever they show. If you remove them, you don't get to put them back.
Because I HATE when a translation (either fan transletion or official. they do this, too) decides to change it mid-series. I hate that I have to re-adjust my brain (as you can guess, I hated whenever I had to change fan translations)

After that... case by case.
I honestly don't mind if FMA drops the honorifics, since almost the entire cast is supposed to be european (except maybe Ishvalans, but you get my point. they weren't supposed to be read as japanese either). However, I think something very clearly set in japan (outside of High-school manga... say... a series set in medieval japan) should keep it, or at least keep the manner of speak as much as they can.
If the story relies heavily on relationships and that sort of thing? then yes, the honorifics are probably an important part of the story that are intended to pass on a meaning that would be lost otherwise.

Then there is certain words (Keikaku). Mostly... I think you should translate them... if the translated word sounds cool. Keikaku is ridiculous, but I will admit I preffer when One Piece keeps "Nakama" instead of "companion". Since I feel the literal meaning (ciompanion) is translated effortlesly and the intended meaning (that of friends so important to you, you are willing to declare war to the whole damn world for their sake) is also conveyed better than if it was translated.

Likewise, there are words for complicated concepts that just have no translation in other languages (not just in japan. most languages have at least one word that is untranslatable).
For example, I distinctly remember the 2003 adaption of Astro Boy kept the word "kokoro" as the thing that made robots like Astro special and why they were true AIs with the ability to grow, which would probably be really hard to convey otherwise.

"Senpai" is also a word I feel should be kept most times, even if you remove Kouhai, since it is a word that is easy to understand and conveys an important aspect of the relationship.

Translations should respect name order. I mean, if FMA can bother to have it's character's names by in the western order, I think the translation team can bother to keep the japanese order and assume the readers won't get confused (altough, if the story is set outside of japan, yes, go ahead and change to the western order).

In short, I don't think it is a matter of wether one is "better" or prefferable, but that those kind of changes should be done on a case by case basis, as with most translations.

That being said, I much preffer to hear "onii-chan" than "big Brother".