Which instant root-touch up is best - powder or spray?

Just like dry shampoo, root touch-up is another one of those time-saving hair products we don't know how we ever lived without. While I don't mind dark roots on my highlighted blonde hair, I hate the look of greys coming through. About 10 years ago, I remember getting a friend to bring me back some Rita Hazan root spray from the US - at the time it was a unique product with nothing else like it on the market.

Fast forward to today and all the mass-market brands have root touch-ups - you can even get it at the supermarket. I use L'Oreal Magic Retouch, $14.95, in blonde, but I also have long relied on Color Wow Root Concealer, $44.95, the first major root powder on the market (there are now a ton of copies of this too). 

There are pros and cons of both, but overall Color Wow is still my ultimate fave. While the L'Oreal spray is much cheaper and also faster to use, I find that the spray doesn't match my hair colour quite as well. It also leaves a bit of a residue, meaning that I'd need to wash my hair the next day (it makes it feel a bit grimy at the roots.)

    Before & After - Color Wow  

I usually try to avoid washing my hair more than once weekly, so the spray only comes out when I'm in a rush and need coverage asap. L'Oreal has also come out with a more precise product with an applicator like a mascara brush, but I haven't tried that yet. 

  Before & After - L'Oreal 

Color Wow takes longer to apply but it does blend better with my hair colour, and it feels weightless at the roots. I can use it without having to wash my hair the next day, and it stays on too. (Apparently it has some special molecule that will only dissolve when properly wet.) I can't speak to any of the dupes/knockoffs of Color Wow but I would say that, just because the package and brush is in exactly the same shape, it doesn't mean the powder is as fit for the purpose. You don't want to be just putting eyeshadow-type powder on your hair, because it won't stay put in the same way as Color Wow. The original costs a lot more, but it does last a really long time (whereas most root sprays probably only have about 20 applications.) I think this was even a problem for the makers of Color Wow at the outset - people loved the product, but weren't repurchasing it, simply because they didn't need to restock for years. 

Which root product is your holy grail?