Experienced chess players know that different players have different "styles".

Player A can win against player B,but player C wins against A but not B.

There may be one or more of several factors. But, for the moment: aggressive vs. defensive?

My first priority has been to get the pieces developed and build a solid defense before attacking.

Often, this serves me well. Yet many other times, the aggressive player who launches an immediate assault does an awfully good job of preventing me from developing and setting up a defense.

So, what do others think? Assault first or defense before assault?

"The best defense is a good offense, (Key word, "good") I think that if you can be aggressive  in a way that restricts one's opponents ability to develop while organically developing one's own pieces, go for it. Be careful not to spread yourself too thin or leave holes in your defense though, so you don't end up suffering defeat from a flanking maneuver...

If an aggresive player launches an immediate attack against you without suitable preperation--then with correct play--he should lose.

One needs to prepare for an attack.

The only way a attack will work without preparation is when the person attacked has made a serious mistake.

In chess, it is best to look for the very best move each move and for that you take into consideration all chss variable and attack and aggression are just two of these.

Your primary assumption is not a given.  I remember someone - Schiller I think - writing that below master level there is no such thing as style, any perceived style is in fact a weakness in a player's game.  e.g. a self-identified positional player avoids tactics because they lack either the ability to calculate or the confidence that they will be able to outplay an opponent in an open position... that Petrosian is known as a slow positional player because of the way he played other top GMs, but he also had the tactical ability to blow a normal master out of the water, etc.

I don't know if I personally subscribe to this, just throwing it out there.

Green, you are correct.

To clarify, the only part of the above statement that gives me pause is the "below master level" part.  It makes the statement sound rather elitist, like there is a magic barrier at 2200 below which a player's game has no personality - either you can see the objectively best moves in the position, or you cannot.

However, I know that the advice is good.  Anyone who sheds a preconceived notion that they can't play a particular type of position - and is willing to put in the work to learn that type of position - will get better.  This is not limited to opening theory of course, but opening theory is the part of the game where it is easiest to impose a 'style' on yourself - which will turn out to be a mistake in the long run if you create an overly narrow range of hands you're willing to play.

Well, these are all good comments.

One player whom I've played at our now defunct chess club would play a solid positional game. Then, somewhere along the way, his opponent would make a less than ideal move. He would take advantage of the situation and maybe pick up a pawn.

Nothing unusual about this. But, when he would get a piece (or the equivalent in pawns) he would say: "And now we start to simplify."

Then he would start trading down. That was his strategy. You work on positioning or tactics and he will trade you piece for piece until you are in an end game and his three point advantage gets greatly magnified.

This was his style. And, it was very effective. 

Then, we have guys like the Parham advocate...jump starts out of the shute with his Q (which we all know isn't generally a good idea) and goes for a quick kill...maybe a scholar's mate. And, that may work very well if played against a beginner.

Yes, a good all-around chess player should be able to do well regardless of "style". But, I know from experience...working up a chess ladder, for example, that A beats B...and C beats A but not B.

I'm speaking in general about middle level chess players, not top level players. About top level players, I am ignorant and freely admit so. lol

This is not a style ... this is just good chess

Well, I also "whittle down" when it seems to be the best strategy. 

But, I would still call it a "style". After I've played this fellow a few times, I know exactly how he's going to play and how I can best play against him. For, I know his "style".

Since you claim "style"  doesn't exist below master level, then what do you think about this piece?

http://chess.geniusprophecy.com/chess-styles.html

Or, how about Chessmaster and how you may play against a wide variety of "styles":

Ginger: offers traps in opening

Guillaume: attacker

Josh: Tough in endgame. Vulnerable openings

Marie: Pawn hunter

Jon: values bishops over  knights

Slick: likes Sicilian

And, etc.