Whats a greenslide?
Is it a wand glide supplied by Greenie?
If its a glide you talking about - yes, it will make the job easier. But really, Derek says they only for girls!
As for leaving carpets drier - thats open to differing opinions.
3 types of glides that I know of - holes, slots, and a hybrid made up of holes and slots.
I prefer the slots, but again open to differing opinions.
There are also cheap glides and more expensive ones. Reports say the cheap ones are not so good. I have a Greenie - not a cheap one but a good one.
Glides are not so much an advantage with portables as with TMs due to the power of the TM, but you may still find it advantageous with a 3 vac porty.