"As regards," "in relation to," "in reference to," "in regard to," and "in respect to." mhmm, and maybe use them in a sentence?
I believe they basically all mean the same thing. There may be a slight difference for "in relation to" and "in reference to", in that the comments are not directly connected to the subject, ie, the comments are generated by the original but don't bear directly on it. I don't believe most people would recognize any discernible difference in meaning, however.
You want your writing to be concise, and those are generally wordy, as compared to "concerning," "regarding," "about," "in," and "with." "In regard to the memo I sent" vs. "Regarding the memo I sent" The second one is a better choice. Source: http://grammar.quickanddirtytips.com/in-regard-to-vs-in-regards-to.aspx
It would depend on the context, though. If it's in dialogue, or the text of a letter between friends or people who know each other well, then yes, I would go with the latter, as you state. However, if this is the text of a business letter or a letter regarding some important matter between relative strangers, I would opt for the more formal (longer) version. Basically it would depend on how the author wants readers to see the relationship between the characters.
I see both shadow and nick's points. I write quite formal passive technical documents a lot at work for government contracts and operational procedures and what-not and, though bland and generally as boring as dishwater, I try to avoid the unnecessary jargonic word count as much as possible. "As regards" - I don't like it in an sense. "As regards the use of the letter S vs the use of the letter Z in the suffix -ise / ize we find...." "in relation to" can fit in a number of situations - "The ship was moving parallel in relation to the major orientation of the orbital base..." or "In relation to your proposed marriage annulment..." "in reference to" is more specific than above I think - "It was in reference to the murder that he pulled me to one side" or "in reference to the input-output port identified as port A, be aware that excessive force will break the connecting pin." "in regard to" is a bit of both - "In regard to your petition for live chicken transplants, the government feels..." or "It was in regard to Joan's excessive alcohol consumption that we all attended the meeting." "in respect to" - Hmmm I dont like this one either - not that I like any of them much - "In respect to the issue before the court.." I may or may not be completely wrong in at least one or all of the above but I gave it a stab anyways based on my knowledge. I'd go with Nick though on this one - They are wishy washy lenghy jargon that can and proably should be better replaced with something else and a quick look at my grammar reference material says the same. If you are determined or NEED to use them, there are plenty of idiomatic dictionaries online that will provide a more concise idea of the meaning and relevant contexts than I could provide here.
ditto all of the above aside from the personal preferences... all the basic info given above is correct...
