I agree with Kinnerley, out of all the AEGs the ICS is superb, mine is my favourite ever gun by a mile and I've had at least 9 different guns over the years.
The G&G and Army versions have blowback mechs which just cause unneeded problems and the Ares is terrible in every possible way, I had one before my ICS and it actually made me hate L85s for about year because it felt so... crap? The performance was awful.
You can run the ICS stock and it'll be fine, it also comes with two hi-caps, the Ares comes with one mid cap. The ICS can take a large battery, which is easy to place, the Ares can only take small ones that are a bitch to place... The ICS has an adjustable spring, the Ares doesn't...
I could go on.
If you're going to get the WE, get the RA Tech upgraded one, it'll cost you a bomb but it won't be as crap. Also, you can get CO2 magazines for it, so you could use it in the colder months, the RA Tech mod even comes with an NPAS fitted so you don't have to worry about it firing too hot when it's warm.
You'll need over a grand spare to fit the parts as they break though, because they will. Not to mention the cost of magazines, gas, lubricant etc etc.
ICS all the way.