You know, reading the "professional" translations may be good for a target audience of casual English-speakers, dipping their toe for the first time into the wacky, madcap world of Japanese comic books, but for more persistent fans of the media--those of us who spend time hunting this stuff down, and who might be following many dozens of titles--these "professional" translations are usually a big step backwards.
First, there is always aggressive localization, changing things that are too Japanese into forms that Suzy and Billy Murica won't feel confused or threatened by. Second, there is always a thorough linguistic scrubbing, taking everything that might not sound familiar to Western ears into the nearest equivalent...even if there is no real equivalent. I'm sure you all know what I'm talking about, but let me toss a few examples out there anyhow.
Let's just take the concept of elder brotherhood. Who you call your big brother and how you call him that matters. Onii-sama is very different from nii-chan which is also very different from aniki. The level of respect and emotional distance is carefully delineated by word and honorific choice, but the "professional" translator would just translate them as some variation of "big brother" wiping away all the important nuance. The other side would argue that if they are doing their job properly, then they are conveying all those nuances in the word choices and phrasing of the words in the surrounding context. If that is true, then I have never seen them doing their job properly. Not to mention that in the West, going around calling your big brother "big brother" all the time sounds contrived and forced. The inclusion of the actual Japanese term in question mitigates this by reminding the Western reader that these characters are hewing to Japanese social norms, where such forms of address are commonplace and natural.
And the example of familial terms pales in comparison to the attempts to translate honorifics into their English equivalents. Guess what? There are no English equivalents! Trying to translate -chan, -san, -sama, -dono, -sensei, -senpai, -chi, and all the rest into Mister or Miss or Lord or whatever does not work. Westerners are getting more and more detached from using honorifics in most cases, but in Japan, all of this is tightly woven into the culture and the language. It would be as futile as trying to translate Japanese foods into their nearest English "equivalents". When you translate honorifics into the nearest English equivalents--even reasonable equivalents--the dialog sounds all stilted and weird, just like with the "big brother" example. And if you elide the honorific altogether and try to imply the equivalent tone through context, you lose a lot of social signalling that those honorifics communicate.
This is why I much prefer "amateur" translators who do this more as a labor of love. They want their audience to experience the works with as much fidelity to the original language and culture as possible, even if it means they confuse that 0.1% of their audience who just started reading a manga for the first time. Once you get past the learning curve (probably with the help of lots of googling) you never want anyone to slow things down to explain to your what "ojou-sama" means, or why a person might give their gender away by using "boku" or "watashi". We may need to be occasionally reminded about the difference between dorayaki and taiyaki if the characters aren't actually eating them, but most of us want as little of a filter between us and the source material as is possible.