Validate ID value by Regular expression or xml.etree.ElementTree

Problem Statement:

I have to validate ID value of all elements in the HTML content. ID value rule is:-

ID value must begin with a letter ([A-Za-z]) and may be followed by any number of letters, digits ([0-9]), hyphens ("-"), underscores ("_"), colons (":"), and periods (".").

Code by Regular expression

>>> content
'<div id="11"> <p id="34"></p><div id="div2"> </div></div>'
>>> all_ids = re.findall("id=\"([^\"]*)\"", content)
>>> id_validation = re.compile("[A-Za-z][\-A-Za-z0-9_:\.]*$")
>>> invalid_ids = [i for i in all_ids if not bool(id_validation.match(i))]
>>> invalid_ids
['11', '34']

Code by xml.etree.ElementTree parser:

>>> import xml.etree.ElementTree as PARSER
>>> root = PARSER.fromstring(content)
>>> all_ids = [i.attrib["id"] for i in root.getiterator() if "id" in i.attrib]
>>> all_ids
['11', '34', 'div2']
>>> id_validation = re.compile("[A-Za-z][\-A-Za-z0-9_:\.]*$")
>>> [i for i in all_ids if not bool(id_validation.match(i))]
['11', '34']
>>>

It also one line by lxml, but exiting code NOT use lxml lib due to some reason.

>>> from lxml import etree
>>> root = etree.fromstring(content)
>>> root.xpath("//*/@id")
['11', '34', 'div2']

The input content contains 100000 of tags, so which is above process best for performance?