Well, lets look at both guns, while we wait for someone who owns one of them to put some input.
http://www.airsoftgi.com/product_info.php?products_id=3436FPS 340-360
Magazine Capacity 450
Accuracy at distance 120 feet
Price 199 (Before tax/shipping)
The Magazine for this gun: $20
http://www.airsoftgi.com/product_info.php?cPath=60_61&products_id=4257http://www.airsoftgi.com/product_info.php?products_id=3629FPS 400
magazine Capacity 300
Accuracy at distance 120 feet
Price 160
I THINK this is a compatible mag for this rifle. But please someone check for me:
http://www.airsoftgi.com/product_info.php?cPath=60_61&products_id=2165Is so, $12.50 is a good deal, although I say not to always trust the cheaper deal.
Now, these states are all based on the airsoft gi website, so I think we can assume that they are accurate when compared to each other. It appears based on these, that the JG M16A4 is the better rifle. It has at least 40 more FPS, the same accuracy for distance, and is $40 cheaper.
But on the other hand, that A&K
Full Metal SR-25 just looks so cool!
Now, after looking at both of these rifles and their magazines. I suggest the A&K SR25, why? because I don't trust anything that sells cheap parts or accessories. In my opinion, based off of a few purchases airsoft and non airsoft. I say that spending the extra money will be worth it.
Of course, this is just food for thought while you wait for someone who owns one of these to reply.
~AFU
Edit: And just for comparison, I'll post the airsoftgi link to a few others of those mentioned.
http://www.airsoftgi.com/product_info.php?products_id=1973