You could do the calculation yourself by using something like
measure-command {invoke-webrequest https://testmy.net/dl-100MB}
Unfortunately, powershell incurs so much overhead that in my brief attempts, I found that powershell was taking almost 10 times as long to complete the download test as wget:
PS C:\Users\Jon> measure-command {invoke-webrequest https://testmy.net/dl-100MB}
Days : 0
Hours : 0
Minutes : 1
Seconds : 26
Milliseconds : 368
Ticks : 863686547
TotalDays : 0.000999637207175926
TotalHours : 0.0239912929722222
TotalMinutes : 1.43947757833333
TotalSeconds : 86.3686547
TotalMilliseconds : 86368.6547
vs
C:\Users\Jon\Downloads\wget-1.11.4-1-bin\bin>wget https://testmy.net/dl-100MB
SYSTEM_WGETRC = c:/progra~1/wget/etc/wgetrc
syswgetrc = C:\Users\Jon\Downloads\wget-1.11.4-1-bin/etc/wgetrc
--2015-06-05 06:18:47-- https://testmy.net/dl-100MB
Resolving testmy.net... 75.126.52.197
Connecting to testmy.net|75.126.52.197|:80... connected.
HTTP request sent, awaiting response... 200 OK
Length: unspecified [text/html]
Saving to: `dl-100MB'
[ <=> ] 104,936,653 10.5M/s in 9.5s
2015-06-05 06:18:59 (10.5 MB/s) - `dl-100MB' saved [104936653]