is Replace() faster than Regex.replace() ?

[wengang]

hi all.
I've been implementing regular expressions throughout my project this week, and I've been surprised by how much faster it processes string tasks.

But this time I found one where Replace is working much faster.

I have an array of 5000 different characters that will be replaced by 5000 other characters.

The loop looks like:

For t = 1 To 5000
            'strText = Replace(strText, Old(t), New(t))
            'strText = strText.Replace(Old(t), New(t))
            strText = Regex.Replace(strText, Old(t), New(t))
  Next

With the first replace, it's a bit slow (1 minute for a 1mb document)
The second one does the same file in about 20 seconds
but with the Regex.replace, after more than 1 minute, I stop the app and it is on t=240 or so.
Why?
everywhere else I've tried, the regex.replace was faster.
Could it be the character encoding?

Second question....
I am trying to do a regex.replace (different one) where the find string may span across more than one line of text
so I tried:
sText = Regex.Replace(sText, "<ut .+?ut>", "", RegexOptions.Multiline)
but that does not do it.
I tried:
sText = Replace(sText, Chr(10), "")
sText = Replace(sText, Chr(13), "")
sText = Regex.Replace(sText, "<ut .+?ut>", "")
and that does work. But I read that regex could search and replace across lines, and I assumed this parameter was it.
How can I get this to replace when the target Text looks like this:
<ut sdfdssd>fdsfsdfsdfsdfsdfsdfsdfsdf
</ut>dsfsdfsdfsdfsd

?

Thanks
Wengang