My inclination is that ご覧になっている is prettier keigo than 見ていらっしゃる. This link turned up in a Google search agrees with my instinct.
「見る」の尊敬語は「ご覧になる」ですよね。では、「 見ていらっしゃる」「見てら... - Yahoo!知恵袋
Summary: Guy asks which is better keigo, 見ていらっしゃる or ご覧になる. A crapload of incredibly pedantic natives say "they are not comparable because one means 見ている and the other means 見る". Obviously this is correct, but equally obviously is the fact that the person asking the question was hoping to have 見ていらっしゃる and ご覧になっている compared.
If you wade past that, you get the answer that the prettiest is ご覧になる. Then you get guys asking if ご覧になっていらっしゃる is better, but someone else saying it's a "double keigo" and sounds wrong.
My opinion is that ご覧になる is bestter than 見ていらっしゃる because you're applying the keigo to 見る instead of いる. Additionally, ご覧になる just sounds prettier than anything 〜ていらっしゃる. It just makes me think of いらっしゃいませ！
