Can't we use 'advice' between colleagues? I and my colleague work in an international company and we are not both English-native speaker but use English for e-mail to each other. I sent to her 'if you take my advice...' because I felt she should take some action for her task. However, she complained that how I could say 'advice' even though I'm not a boss to her. Was it wrong?
If I've got your question right, you are asking for a more polite way to communicate with your colleague ?
Why not use "probably it would be good to check this and that at first" for example or "wouldn't you agree ?" instead of a discussion on advice.
advice and suggestion are almost synonyms. The difference is that advice is stronger, implies that the solution is better than others. Suggestion can be also seen as "aggressive" by some people - on the principle of: "What?! You think you are smarter than me?"
While exact words are not essentially important, you can use something along this:
My choice would be to [solution], but other solutions may work equally well.
Neither "advice" nor "suggestion" implies something going from a boss to a subordinate. If anything, both imply something moving between approximate equals, or from someone in a lower position to someone in a higher position. A boss gives "directions", "instructions" or "orders" to a subordinate -- things that the subordinate is required to follow. A boss may also give advice, but such advice will carry added weight because of the authority of the person who gives it.
From someone who is not a superior, "advice" implies a plan which the giver seriously recommends or urges the receiver to accept and follow. A "suggestion" on the other hand, is merely offered for consideration, and the giver may not be seriously urging the receiver to follow the suggestion. It may also be less detailed than "advice" would be. However, the two words overlap a good deal in meaning, and personal style may favor one over the other when a different person would make a different choice.
In any case, there is nothing improper or impolite with one person saying to a colleague "My advice would be to do X" or "I would advise you to do X" or "If you take my advice, you will do X". None of these purport to order the listener to do X, at most they recommend or urge X.
I frequently send email to work colleagues saying things such as: "My advice would be to adopt solution X" or "I advise that we do X".