Which is harder for you to play against.  A person with a competitive rating to yourself or someone that is new to chess or doesn't know tactics/theory behind why pieces are played the way they are played.  Although this question might seem like it has an obvious answer, I'm wondering if playing against a newer player might be harder because their movements being more erratic and less predictable than a high ranked experienced player.  Also someone playing a very erratic game might not have the best defensive position but by moving pieces out of sync to your movements might force you to make moves that you wouldn't normally make thus getting you out of your own pace?

I would still say begginers. The reason that moves you don't expect to be made aren't made is because they allow for you to take advantage of them. This should allow you to win easily.

Maybe it sounds overly simplistic, but a person with a good knowledge in openings, tactics, positional play, and endgame play will always be harder to play and win against than a person who has no clue what he or she is doing.

Like you said, a newer player will be erratic and less predictable, but that doesn't make them challenging; instead, it makes them easy.  It doesn't matter how random the position gets: if they drop a lot of material against me, they'll lose.

"more erratic and less predictable" mostly means just bad, so of course it's much easier to play beginner.

Yea luck doesn't have too much to do with chess.  An erratic beginner would lose to an 1800+ player 99.99999999 % of the time whereas the chance of losing to a competitive similarly rated opponent would be around 50%.

"More erratic and less predictable" mostly makes it much easier to fulfill a plan, so it makes it easier to win.

Well.. i'm not sure that i was 100% clear in what I meant.  I'm not saying meaning in regards of beating an inexperienced player so much as being able to execute tactical movements that require an opponent to make certain moves.

When you spot a possible tactical manouevre it should be robust enough to cope with any move combination. If an opponent makes an unexpected or erratic move it should make his position even worse than if he made the expected move.

Say I spot a combination that wins a rook, but my opponent replies in an erratic fashion - I might win the rook + 2 pawns or a queen instead or just win the rook, but then flow into an unstoppable mating combination immediately afterwards.

If the unexpected move gets my opponent out of the tactical manouevre then it was my fault for not spotting the escape and I'll try harder next time.

The chances of my losing to a patzer are about the same as my chances of beating a GM.  About 0%.  The chances of losing to a player plus or minus 200 points are about 50%.

hmm...are you a poker player by any chance?

beginners are definitely easier, they have nowhere to hide.

Novice poker players are very dangerous..

They often call and raise in unexpected situations.

Once a King,always a King but a knight only once.

The only chance beginners have is if you get too bored with the game due to the fact they don't ever resign.

Unexpected moves against a beginner are because they overlooked something.

Unexpected moves against a strong player are because I overlooked something.

Which do you think presents more of a problem?

It is not to hard at all compared to stronger players, especially if the stronger player is solid in all area's of the game.

A good player ALWAYS has a plan (a bad plan is better then no plan at all they say) So evaluate whether their random looking move influences ur plan or not, if it doesn't then continue with ur plan, if it does then spoil their moves.

Sometime i find it fun just to cut their options out especially if their pieces are uncoordinated and by doing that you give them more options to make big mistakes and they fall apart from not knowing what to do.

The problem with beginners is that you find yourself looking and worrying about situations that they can't see.  This can lead you into missing the obvious. It shouldn't but it does. Ooops, I just read the part about 1800, I shouldn't be here, I'm not rated anything.