Just used `Thyme` (https://github.com/Ichoran/thyme) for a quick micro benchmark. See results below. Quick upshot is that `ListBuffer` is slightly faster than `Vector` for append operations, but ends up generating more garbage. My guess is because at the end you would want to return an immutable version to float throughout the rest of the system and the ListBuffer `result()` method is expensive space-wise.

```scala
scala> val th = new ichi.bench.Thyme
th: ichi.bench.Thyme = ichi.bench.Thyme@1268bfa2

scala> val nums = 0 to 100000
nums: scala.collection.immutable.Range.Inclusive = Range(0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111, 112, 113, 114, 115, 116, 117, 118, 119, 120, 121, 122, 123, 124, 125, 126, 127, 128, 129, 130, 131, 132, 133, 134, 135, 136, 137, 138, 139, 140, 141, 142, 143, 144, 145, 146, 147, 148, 149, 150, 151, 152, 153, 154, 155, 156, 157, 158, 159, 160, 161, 162, 163, 164, 165, 166, 167, 168, 169, ...

scala> def appendWithVector(nums: Seq[Int]): Seq[Int] = { var v = Vector.empty[Int]; nums.foreach { v :+= _ }; v }
appendWithVector: (nums: Seq[Int])Seq[Int]

scala> def appendWithListBuffer(nums: Seq[Int]): Seq[Int] = { val b = mutable.ListBuffer.empty[Int]; nums.foreach { b += _ }; b.result() }
appendWithListBuffer: (nums: Seq[Int])Seq[Int]

scala> th.pbench { appendWithVector(nums) }
Benchmark (1260 calls in 11.07 s)
  Time:    4.196 ms   95% CI 4.037 ms - 4.356 ms   (n=20)
  Garbage: 3.998 ms   (n=591 sweeps measured)

scala> th.pbench { appendWithListBuffer(nums) }
Benchmark (10220 calls in 139.0 s)
  Time:    3.859 ms   95% CI 3.818 ms - 3.900 ms   (n=20)
  Garbage: 8.552 ms   (n=1147 sweeps measured)

```