MySite should have its own WebApplications and Blog is subweb for each Personal Mysite.
I created this script, hope help you
asnp *sharepoint*
cls
$WA = Get-SPWebApplication https://my.dev.cz
$global:BlogsCount = 0
$global:MySiteCount = 0
$global:MySiteCount = $WA.Sites.Count-1
foreach($Site in $WA.Sites)
{
Write-Host $Site.Url -ForegroundColor DarkYellow
$Web = Get-SPWeb $Site.Url
if ($Web.Webs.Count -gt 0)
{
$Blog = $Web.Webs | ? {$_.Title -eq "Blog"}
if($Blog.count -eq 1)
{
$global:BlogsCount++
}
}
}
Write-Host "Total count of MySites: $global:MySiteCount" -ForegroundColor Yellow
Write-Host "Total count of Blogs: $global:BlogsCount" -ForegroundColor Green
If you need some edits, feel free to contact me :)