I have worn my grills for 2 out of my 2.5 years of playing. Loved them, but I have a massive gripe about the amount of money I have to shell out for lenses!
They have great air circulation, good vision and good protection on either side of your head but they ain't so good for the forehead shots!
I have now owned my shiny limited edition Profits for a month now. They in my opinion have better vision, a better lens and sightly better forehead protection. Oh and the protection you get to protect your goggles from rain isn't too bad either. The strip of plastic that goes across the top of the air vents is one of the better designs (moving away from the ridge cap from the grills).
I do find that it isn't so much the hearing that is the problem, but the rebound of sound from the goggles to my ears which might be a slight problem, the way the goggles are curved back (towards your neck when wearing them) at the front means that the air circulation feels a little lower then the grills, but once your play you don't obviously notice. The noise ridge on the slys seem a little higher as well, but once again, everytime you change goggles you notice the ridge height difference!
I was talking to someone over this weekend who just bought the profits and he can't handle with how uncomfortable the ears are, it may be user error but I have been told you can rip these foam ear parts off, obviously when you do so they cannot be simply be glued back on!
Overall for the price and economy of the grills to profits, the profits win, they seem more durable (the rubber that loops behind the strap had broken off my grills within owning them for about 2 months).
The lens on the Profits are in my opinion are of superior quality, being double skined like i3's, but every retailer are selling the lenses at a pretty sharpish rate so getting hold of spares may take a little waiting if you don't like the ones that come on your new profits.
The double strap on the profits are incredibly helpful for me as I wear glasses in x-ball, it allows me to take my goggles off without having to loosen the strap adjustments (as on my grills) but I can simply leave them on full lose adjustment and they will sit hold on my face through dives.
If I was a sponsored Sly guy then this does sound rather biased, but I like wearing my Slys more then my grills, they are new and shiny - every man deserves something new and shiny!