I'm accustomed to playing wargames that have graduated wins. Most extreme is the 20-0 system, where a draw is a 10-10 and there are graduations of win/loss up to 20-0. These sorts of issues apply to most competitive wargames.
Only Win/Loss:
Pro: sure makes tournament rankings easier and eliminates the whole ID issue.
Pro: works for elimination (e.g. top 8 cut)
Con(?): promotes "alpha strike and run away" type armies. (For some game systems this can be an issue, not sure about X-wing)
Con: no acknowledgement of the level of victory, there's something different about a close game between equal players and a total floor wiping. (Again, may not be a "con" to some people)
Con: requires a tie breaker secondary calculation (i.e. MOV)
Con: in a true draw situation, requires a fairly arbitrary tie-breaker (e.g. player with initiative). Having what is truly a honest draw settled by the pre-game coin toss is unsatisfying to say the least!
Win/Loss/Draw
Pro: requires a win to be of an appreciatable margin
Pro: allows for a situation where neither player has the upper hand to be reflected in scores
Con: situations where both players are happy to draw, scores are very predictable
Con: still requires secondary scoring system (MOV)
Points based (e.g. 20-0, modified wins, even pure MOV scores)
Pro: rewards both winning big and preventing losses
Pro: rewards conserving points in a loss and not just conceding (this can be a "con" too, if a player is forced to play out a game they'd rather just concede)
Pro: with enough granularity, does not require separate MOV recording.
Con: a player with a few big wins and some narrow losses can do better than a player with all (narrow) wins
Con: concessions can badly skew results