-Name is a convenient switch to only output item names (without -Recurse) or relative paths (with -Recurse).

Given that only string instances rather than System.IO.File/DirectoryInfo instances are output, one would expect -Name to speed things up (or at least not to slow things down); however, with -Recurse present, -Name slows down the command noticeably.

Steps to reproduce (on Windows)

# Warm up the cache
$null = Get-ChildItem -Recurse 'C:\Program Files' 

# Without -Name
(Measure-Command { Get-ChildItem -Recurse 'C:\Program Files' }).TotalSeconds

# With -Name
(Measure-Command { Get-ChildItem -Name -Recurse 'C:\Program Files' }).TotalSeconds

Expected behavior

The command with -Name should be faster (or at least not slower).

Actual behavior

Sample timings:

1.544098   # without -Name
4.5759553  # with -Name

That is, adding -Name made the command about 3 times slower.

Environment data

PowerShell Core 6.2.0-preview.4