collection.rb

start = Time.now
100.times do
  letter_list = []
  alphabet = ('a'..'z').to_a
  100_000.times{ letter_list << alphabet[rand(26)] }
  pick = letter_list.uniq[rand(26)]
  before, after = letter_list.partition{|n| n > pick}
end
p (Time.now - start) * 1000

collection.scala

import scala.util.Random

val start = System.currentTimeMillis
(1 to 100).foreach { _ =>
  val alphabet = ('a' to 'z').toArray
  val letterList = (0 to 100000).map( _ => alphabet(Random.nextInt(26)) )
  val pick = letterList.distinct(Random.nextInt(26))
  val (before, after) = letterList.partition{ _ > pick }
}
println(System.currentTimeMillis - start)