To be fair I haven't seen too much of Voigt, except when he's been doing the Savoldelli role on the motorbike or the very occasional visit he's had to the commentary booth, but in English he always has his 'funny persona'. Which can be very entertaining, I remember he did a really funny interview in the 2009 TdF explaining how Astana could be beaten. But ideally I want commentators to either be chill or serious sometimes as well.
He does have his 'funny persona' on German TV as well, but it's not all he will bring in to it. He often empathizes a lot with the riders, he will express when he is concerned as he expresses when he is exited. Though he's truly not your ordinary expert or commentator, but he does bring in a human quality that is often lacking in super professional, but sometimes sterile commentary.
In GTs German ES basically runs the commentary as a Cycling Talkshow+Live commentary with 3 commentators, a person for culture and landscape plus an extra guest once in a while. So Jens is a coulorful sparkle in that picture. It's a bit different when he's doing 50% of the commentary, but I personally still enjoy it. Also because sometime it makes me check the race situation as he either points out something I totally overlooked, or he points out something only he has seen or thought about it, so in a weid way he contributes to my race awareness while watching.