Personal opinions vary, of course, but I like the roof mounted antenna. Or at least I prefer it to the other options. Since it is angled, it appears somewhat aerodynamic... You can buy a shorter roof mounted one if yours is too long. You should decide what YOU like instead of what your mechanic likes.
If you decide that you want to replace it, since I live in Europe I could easily and cheaply find a replacement roof-mounted antenna... I've sent them to others who liked the look...
FWIW
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