String start_with? vs [0] ==

gistfile1.txt

Calculating -------------------------------------
     str.start_with?     78491 i/100ms
       str[0] == '/'     66410 i/100ms
-------------------------------------------------
     str.start_with?  3663514.9 (±7.8%) i/s -   18209912 in   5.002869s
       str[0] == '/'  2905683.6 (±7.6%) i/s -   14477380 in   5.011908s

Comparison:
     str.start_with?:  3663514.9 i/s
       str[0] == '/':  2905683.6 i/s - 1.26x slower

stirng_strart_with_vs_first_char.rb

str = "/lkasdjglaskjdg"
Benchmark.ips do |x|
  x.report("str.start_with?") {
    str.start_with?('/')
  }
  x.report("str[0] == '/'") {
    str[0] == '/'
  }
  x.compare!
end