A Scottish once solicitor told me that in law capitals or lower case don't normally mean anything different; a it's simply a matter of family custom and preference. Just like Mc and Mac mean the same (this is comping too late to the party, but very well done FrancisCrawford and supporters on that topic; I wholeheartedly agree.)
In the past, in Gaelic speaking areas, the word following the Mc or Mac would usually have been capitalised of course, since it was a proper name.