The Helix is obviously a better unit to buy if you can afford it buy it. The HD 500's are great there's loads of flexibility with sound and it's down to how you decide what sounds right for you so you need to spend some time to form your sounds. IMHO you won't get a better piece of kit for the money . The only issue you will find with Line 6 is the back up service is pretty poor, if your unit breaks down you will struggle to find a repair shop if you are in the UK , My HD 500 board has just gone and I have to right it off because the cost of a new board is more than the pedal is worth. despite this I'm sticking with them because they work well for me . All kinds of factors come into sound , I think in the end you pay your money and take your chance and as a previous responder said if it doesn't work out sell it.