Is it faster to append, or to just assign in place?

foo.go

package main

var sliceOf20Ints = []int{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9}

func toIfaceWithAppend(ints []int) []interface{} {
	var ifaceInts = make([]interface{}, 0, len(ints))
	for _, someInt := range ints {
		ifaceInts = append(ifaceInts, someInt)
	}
	return ifaceInts
}

func toIfaceInPlace(ints []int) []interface{} {
	var ifaceInts = make([]interface{}, len(ints))
	for i, someInt := range ints {
		ifaceInts[i] = someInt
	}
	return ifaceInts
}

foo_results

Christophers-MacBook-Pro:tmp cagocs$ go test -bench=.
testing: warning: no tests to run
PASS
BenchmarkAppend-8 	 2000000	       710 ns/op
BenchmarkInPlace-8	 2000000	       718 ns/op
ok  	github.com/agocs/tmp	4.306s
Christophers-MacBook-Pro:tmp cagocs$ go test -bench=.
testing: warning: no tests to run
PASS
BenchmarkAppend-8 	 2000000	       717 ns/op
BenchmarkInPlace-8	 2000000	       704 ns/op
ok  	github.com/agocs/tmp	4.291s
Christophers-MacBook-Pro:tmp cagocs$

foo_test.go

package main

import "testing"

func BenchmarkAppend(b *testing.B) {
	for n := 0; n < b.N; n++ {
		toIfaceWithAppend(sliceOf20Ints)
	}
}

func BenchmarkInPlace(b *testing.B) {
	for n := 0; n < b.N; n++ {
		toIfaceInPlace(sliceOf20Ints)
	}
}