Airsoftgi.com, you can use coupon codes to reduce the price, you get free shipping over 100 dollars no coupon code necessary, they have a rewards program, they have the largest inventory so the likelihood of your item going back-ordered is very low, if you're lucky you can find amazing price cut deals on items and their customer service top notch. I've bought damn near every item I could from them in the past three years and my team as a whole has probably spent easily thousands of dollars on their website.
As an example, they typically sell the middle line metal ICS M4's for 260, I got it on sale for 180, used a coupon code to bring it to 160, got free shipping, and it got here before the end of the week with a chronograph reading, free t-shirt, some okay safety/game scenario/maintenance fliers, and obviously the AEG I ordered. Just the simple fact that I can use coupon codes AND get free shipping beats almost any other price on websites like evike or airsplat.
My only complaint would be I wish their video reviews were way more in-depth as they typically do not talk about the internal quality of most airsoft guns they review.
Evike and airsplat are occasionally cheaper or have things you won't find on airsoftgi.com. Buy from them at your own risk. Evike has horrible inventory and every time I've attempted to order from them, the item was back-ordered. Not only were they back-ordered, but when I tried to get my money refunded, it took almost two weeks! (Which is better than some stories I've heard of people NEVER getting their money back and receiving the back-ordered item two months later). They also have a very, very, very dark history if you back several years.
I also encountered a G&G Combat Machine M4 that evike.com sold to a player recently I met who was having trouble. Turns out it wasn't a combat machine, it was the older style non-blowback version and had been incorrectly modded using the o-ring trick on the barrel for better compression which in this case created a huge lack of compression.
As for airsplat.com, their biggest failing is in their product descriptions from the times I ordered from them (they've gotten better by including full review sections) and them frequently over-pricing items that are completely outdated (like the old Dboys M4's, that crappy wanna-be DPMS Softair/Cybergun A15, etc.) Their customer service never was really helpful although may have changed recently. I've even read older horror stories of people not even recieving the correct items they ordered, although I'm sure this is a rarity with their new 'make-over'.
In short, go with airsoftgi.com unless they don't have what you're looking for. Some other great websites that have smaller inventories, ok prices, ok shipping, but excellent customer service are airsoftatlanta.com, airsoftextreme.com, and trinityairsoft.com