I can't get them here yet and I don't want to pay all of the various charges for shipping to Canada. I suspect people like them because gels colour faster because there is more liquid in them. I can get the Chefmaster liquid gels and they work well. Wilton's are more of a paste. Hey, whatever works, right?
One thing I would say is that for colouring fondant, well the gels can really add a lot of liquid to the fondant so you get quite a mess and have to add a whole lot more icing sugar. You can't win, you use the gel to get a faster colouring, but you have to keep stopping to add more icing sugar to the fondant. But if you use the Wilton pastes, it takes a lot more to get the colour, but it doesn't get as sticky, haha!
I wonder when Wilton will jump on the bandwagon and develop a more liquidy colour system.