Quote Tony Soprano="Tony Soprano"Wouldn't a non-possession player be offside and not out of play? what's the difference'"
The point is, that is what the laws of the game state, so it isn't up for debate. The player is offside, but he is also out of play. (We know he is also offside, as rule 13 explains how he cannot be put onside; which clearly if he wasn't offside, would be illogical)
The difference is that a player offside is either put back onside or he isn't - it's a straight question of fact. Whereas a player who is out of play at a PTB can't take part in the next play unless "the advantage gained by not retiring has been lost", which leaves it up to the interpretation of the ref.
So, is it better to be "out of play" or is it worse? I think one big clue is in the rule which states that a player out of play is NOT put "on side" by any of the normal events in Rule 13. Why is that important? Well, because even if any of the events occur, such as a team-mate with the ball getting ahead of you, so that you WOULD now be immediately onside, under this rule, you're still not. You still, even then, can't take part unless BOTH (a) you are on side, AND (b) you haven't gained any advantage by not retiring. So I reckon the bar is a level higher.
Whilst the rule does not make a crystal clear dividing line, unlike offside, I would suggest that it is easy enough to judge which side of the line any given incident falls. I don't really see there is any problem in interpretation. If you are hanging about, without having made the 10, but then take a pass as the play progresses past you, the fact you have gained an advantage is plain as day. Including (a) you wouldn't have been there in the first place had you retired the ten; (b) you have taken up and utilised a key position illegally (even if unintentionally), to mention but two.
Given what the rules state, I can't see any realistic way that a player who actually takes up the ball from that position could ever be ruled NOT to have gained an advantage.