So, here is my opinion, for what i's worth!
Pilla
Good products with an excellent range of tints available although the 46N is perhaps the only product in the "new" incarnation that is truly different from the old, perfectly functional lenses.
They don't win points for aesthetics, and some of the original frames could be quite heavy.
They have addressed the weight issue with the new Outlaw X, Fugitive and 500 Series - they have also made them a lot more comfortable with the gel pad bridge - the old nose pieces were horrible.
The lens change system is good - the "poppers" allow a rapid switch without getting them grubby.
They are costly, but generally score well for me as a high end product.
It is worth noting they have a "budget" option, the Hawk, which goes out around £200 for a frame and three lenses. The Panther lenses fit this too.
Beretta and Castellani do similar looking products for a much lower price point but are not as refined.
Oakley
Robust, well made, lightweight. Unfortunately a dwindling availability of product since their takeover by Luxottica. Mframe looks to be phased out very soon and shooting-specific lenses such as G26 are gone forever it appears.
The Radar and Radarlock options do a good job although some people can find the black nose-piece and low brow-bar off putting - all depends on individual face shape and gun position. The Radarlock has a nice easy lens change system, the original Radar can be a devil.
Bottle Rocket and Flak XLJ work very well and the lens change is quite straight forward.
Think in terms of £75 for an Mframe with a standard lens (ie, non-iridium coated, non polarized) and £225 ish for a Radar array with two lenses. Also available from Ebay and discount stores. Be aware of forgeries as Fauxkleys look ok in the photo but feel very cheap when you actually get them!
Where Oakley blast the competition is in their prescription range - wonderful lenses delivered quickly and with great tint choice. Expect to pay £205 to £300 for a set of lenses (frame extra) depending on type.
Randolph Engineering
Versatile, lightweight, affordable. In the same style as Decot and Straub Hi Scorers. I tend to prefer RE and their product support is good.
Great lens choice and everything is glazeable to prescription apart form the XLW which requires an insert.
Expect to pay between £140 and £180 for a frame, £39 for basic lenses and £90 to £120 for Premium options (Polarized and the "astronaut" CMT)
Adidas
Only real option is the T-Sight, actually a golf frame but the lightest of all, no brow bar and good lenses, three for about £189.
Top Gun, Evolution, Jack Pyke products - three lenses and a frame for £40. Do a job, pass all ballistic safety tests. Lens quality and tints are not great but keep the sun out and protect your eyes well so a fine budget choice.
Wiley X
A more advanced version of the above, a good middle ground but not a favourite of mine.
Hope that helps!