I have both. I have to say that the parlux has not revolutionized my life in the way I had hoped ( I have v thick hair). It could be because the lead has gone all kinky and it makes me irrationally annoyed every time I use it.
OTOH I love my GHDs. I got DH to buy them as a birthday present one year and they have lasted wonderfully. I went through two other sets of irons before and they were useless.
However if you don't actually need GHDs then lots of people swear by the parlux.
Like redtartan I have a Parlux hair dryer and ghd straighteners. I love the hair dryer - much speedier and leaves my hair smoother than my previous ancient one. I recI find I need to use the ghds less too.
Oh and my hair looks incredibly shiny. I sometimes use it in the morning in between washes with a round brush to smooth out the bits that have gone a bit kinky where I've slept on it - takes literally a minute to do and it looks fresh as a daisy.
I have both a parlux dryer (it's red not sure on model) and a ghd hair dryer. I much prefer the ghd. It leaves my frizz prone hair much smoother even with just a quick go over with my head upside down.
I've got an ETI hairdryer (too cheap to splash out on a Parlux) - I think the thing is to get a professional dryer of whatever brand and you get about 10x the power of "domestic" ones. Then save up for Ghd's if you think you still need them. I have very thick wavy hair and it's the only thing that has properly tamed it. I dry with a large round brush in sections like the hairdresser does.