Just to break balls, its not really a Mk46, but its close
+1 to what Silent Stalker said about bringing lots of ammo. I went through 18,000 rounds or so at LOWII. Games before then usually average 2-4 bags of ammo per (I've only used it at big ops.
G&P make a damn fine SAW. I've gone through 60k+ rounds with the only problem being the hopup exploded. There have been some external issues. I lost the cotter pin that held the stock pin in (it was my own fault for not inserting it correctly), the whatamadoodle that sits above the charging handle came off randomly, and the box mag broke along the top when it was landed on. Its a weak point in any SAW (and would be a non issue if you could buy new box mag shells from G&P), but since the G&P feeds from the bottom, I had to custom mod a RS mag to work with it, whereas a CA/A&K can just take the guts of the box mag and be crammed into a RS mag. Another thing to consider with the G&P is there is no safety. Its just two buttons glued onto the side of the body. Also, the bipod came off (the legs were made of steel, but the mount was chinky metal) but its a non issue to me since I never used the damned thing.
If I had the money, I'd get the G&P, mainly because its been a great gun and its the only accurate Mk46 on the market. It also has the most RIDICULOUS stock ROF of any SAW out there. Putting an 11.1v lipo in there makes it a machine gun thats firing very angry bees at 400FPS. If I didn't care about it looking like a Mk46, I probably would get a A&K due to the price and that CA guns hate me. Whatever you do get, expect to spend more maintaining it/feeding it than a regular AEG.