Of the providers I have used over the years for broadband, Vodafone have been far and away the worst so I'd swerve them.
My broadband would cut out completely when it rained. Thought it was a coincidence at first, but I called them after the third time and was told it was a "known issue" which they were "working to resolve". Which I know is placating talk for "We don't have a clue, sorry."