What is the main difference between '[[:space:]]' and '\s' in Oracle pl-sql regular expression?
The Oracle documentation confirms that the POSIX expression [[:space:]] is equivalent to the Perl-style \s. I personally prefer \s because it's shorter, and also supported by many text editors.
In your example you have [[:space:]] (one whitespace character) but \s+ (one or more whitespace characters). Maybe that should have been [[:space:]]+.