A couple quick benchmarks:

```scala
scala> th.pbenchOff() { val b = mutable.ArrayBuffer[Int](); (0 to 10000).foreach { b += _ } } { val b = mutable.ListBuffer[Int](); (0 to 10000).foreach { b += _ } }
Benchmark comparison (in 13.19 s)
Significantly different (p ~= 2.602e-11)
  Time ratio:    1.36152   95% CI 1.27677 - 1.44627   (n=20)
    First     79.76 us   95% CI 76.97 us - 82.56 us
    Second    108.6 us   95% CI 103.0 us - 114.2 us
```

```scala
scala> th.pbenchOff() { val b = mutable.ArrayBuffer[Int](); (0 to 10000).foreach { b += _ }; b.drop(500); () } { val b = mutable.ListBuffer[Int](); (0 to 10000).foreach { b += _ }; b.drop(500); () }
Benchmark comparison (in 12.45 s)
Significantly different (p ~= 0)
  Time ratio:    0.55391   95% CI 0.54554 - 0.56227   (n=20)
    First     618.6 us   95% CI 610.1 us - 627.1 us
    Second    342.6 us   95% CI 340.5 us - 344.8 us
```