Preferring Helvetica over Arial is commonly just pure snobbery. There are couple of reasons behind that: Helvetica is associated with Macs while Arial is associated with Microsoft. Helvetica can be argued to be "more original" than Arial. The Arial we usually see (Microsofts version) is heavily optimized for low-res screen display at body text sizes, which some might say compromise it for high-res/print use. Helvetica is also available in significantly more variants than the Bold/Italic MS Arial.

Arial is a sloppy-looking knockoff of Helvetica. It's the typographical equivalent of fake designer clothes.

There's nothing inherently wrong with using Verdana as a screen font.