The AR15 isn't an option because I despise those poorly designed pieces of s--t (the one exception would be an AR with a gas piston).
Have you ever even owned an AR15, Because I only expect this from people who have never owned one and are trying to be a badass or they just cant afford one. The AR system is awesome, you sound like you read a few books, or watched a tv show about the early AR15 and based your opinions on it. Ive been shooting AR's for probably 6 years now and not one of my AR's has jammed as many times as my pos WASR guns. What about it is a poorly designed piece of s--t? I have a hard time finding it. Besides they must have something right since its been our weapon of choice for over 40 years now.
I have absolutely no interest in owning one. I'm a very mechanicaly inclined person, and I have studied both the AR15 and AK47 designs. There is no way in hell I would consider the direct gas defecation system of the AR15 to be a good design.
What disadvantages does a gas piston upper have? Weight? That's the only one I can think of. An extra pound of weight will turn a gun that needs to be cleaned thoroughly after just a thousand or so rounds int a gun that could conceivably run tens of thousands of rounds without a major cleaning. While I would never let my gun go that long without cleaning, I like to know that it is capable of doing so. Cleaning will be easier with a gas piston design as well since the powder wont be caked on and hardened to everything in the upper receiver.
And I am not one bit surprised your WASR jams. It is the very bottom of the barrel as far as AK's go. My chinese made Norinco has been flawless, except for one failure to fire while bumpfiring it because the hammer followed the bolt home.
Just because the military uses something does not mean it is the best. The sooner you understand that the better off you'll be. Atleast times are changing and newer better guns are being fielded (albeit in limited numbers at this time) such as the HK 416, FN SCAR, etc.
I find very few faults with the lower receiver of the AR15. Though, I am not fond of the recoil spring/buffer tube design and would prefer a more traditional spring. My hatred for the design comes from the upper receiver. The gas system is a piss poor design, I don't like the barrel extension or the high number of locking lugs on the bolt. Designs that use an AK type 2 or 3 lug bolt are just as accurate (SIG 55x) and easier to clean.