Everything in the nature of b-wings is to provide a low-deviation. Outcomes are far more predictable as fewer green dice are rolled, both offensively and defensively. There are a few other considerations with b-wings that are a little bit glossed over with a hard-and-fast rule on range.

Get away from the b-wing and look instead at the z-95's durability compared to the tie fighter for another illustrative comparison. The mean shots to destroy a z-95 and tie fighter are the same, within 1-2% depending on the mix of attack strengths you are throwing at them. At the same cost, same firepower, and same mean shots to destroy, the z-95 and tie fighter are fairly interchangeable in effectiveness aside from dial/action differences. However, their distributions of probabilities around that mean are very different. This discussion came up in a local group of mine, but the probability of a tie fighter dying in a single shot, for example, will always be higher than that of a z-95. Every dice roll outcome that can result in a dead z-95 will also include the death of a tie fighter (even if you made an assumption that the extra defense dice always lands evade, which is to illustrate the independence of the 3rd agility), however there are a few more outcomes of dice rolls that have a chance to kill a tie fighter but not the z-95. On the other hand, there are probabilities past the mean (say, the chance of a tie lasting 6 shots pointed at him) that are higher than the z-95's.

Back to the b-wing, who rolls one defense dice, will have a fairly small deviation from its mean shots to destroy. Range 1 will facilitate this even more because it is not adding green dice and instead adding red dice to pin down that low-deviation mean result.

There are some other tactical/strategic considerations why b-wings "like" range 1 (in fact, I am not convinced they really do like it more than other ships). In formation flying, the goal is primarily to engage your like-guns at the same range band, though not to necessarily be attacked at it. Even if you spread the same amount of firepower amongst a greater number of cheaper ships, your effective firepower is likely to be less concerted, as you need to get more ships into the same space to avoid having your shots spread amongst range 1, 2 and 3.

Another corollary not discussed here is the effect of adding adding attack and defense dice to the shifting mean rounds to destroy calculation; the trend follows that if you add attack dice (to a point), the mean rounds to destroy shifts a greater amount if your defender has a higher agility. That extra attack dice in range 1 shifts the mean rounds to destroy of a low agility ships proportionally less than it does for high agility ships.

4 b-wings are equivalent in firepower and durability (by the mean rounds to destroy) as about 6 and a half tie fighters (call it 7, for instance). If it is difficult to get 4 ships into one range band, 7 would more likely be half-spread between one range band and the next.

And, as was mentioned already, PS also matters as the volley nature of the game can mean a ship can be destroyed without response or be forced to lower the quality of its attack if it spends focus defensively, complicating the situation.