Instruction: Extract information from the supporting document to answer the given question.

Input:
Question: What is the better buy?  The 2nd gen 9000 or the 3E, outside of the fact you get an extra 1000mAh?
Document: When you got an Anker product, you got something that radiates premium quality! And thats exactly the case with the Anker 2nd Gen Astro 2 9000mAh.Looks amazing, has a soft touch body that feels very premium.I was able to recharge my nexus 7 2013 2 times from 10% to 100!, and and the charger still had a bit of power. I had a good experience with the Anker Mini and a better one with this amazing portable charger. I highly recommend to buy this charger if you want the best.
The 2nd gen Astro2 is the best or one of the best battery backups I've ever seen, I can charge my phone at full speed like if it is charging with a wall plug, and also because of the 2 ports I can charge my devices simultaneously. The texture of the battery is very smooth and leaves no finger-print and the included pouch is excellent to protect it. When charging my phone the battery don't get warm. 100% recommended. It won't dissapoint you, buy it!
I chose the Anker 2nd gen 9000mAh because my 1 year old iPhone is having battery issues and it drains rapidly and will lose a charge. So far the Anker unit has been invaluable at certain times when an outlet is not an option (Plane), or you dont want to be tethered to a wall.The unit is small enough to fit in your pocket, and has worked on my iPhone, Kindle, and some other Micro USB Android phone. The best feature in my opinion outside of it actually chargin the phone is the circle power indicator to let you know how much juice you have left.Overall the charge speed is good, and the quality seems to be fantastic.
The Charger arrived with no damage during shipping. My Razr HD has a 2530mah battery and I charged it with the phone on each time starting at 30% battery remaining on my phone four times. I was able to charged it fully three times and on the last charge it charged it from 30% to 46% until the charger was drained. Doing the math the Anker 2nd Gen 9,000  should charge my phone from 0% to 100% 2.69 times to a full charge with the phone turned on so I would expect it to do better with the phone turned off.
I don't have a problem with this feature, but if you do there's always the older Astro line that doesn't have it. Personally though, I think it's a no-brainer which is better considering the improved efficiency and power gauge of the 2nd gen line.Output-wise, the 2nd Generation Astro 2 has two ports, a 2.4 amp 5V for charging things like tablets (can step down to lower current) and another one that the included documentation rates as 3A (though I think it's really a 2A- there's not much reason for a 3A as few if any devices support that).
I have bought several other battery chargers the same size or larger capacity than this model and this one is by far my favorite.In fact, I have enjoyed it so much that I even decided to buy a couple more to replace my other external chargers even though there is nothing wrong with those other ones and they still work fine. This model just works better and is better designed ergonomically.
A must buy. So far so good. Not only for the excellent service and customer care, the products are awesome. Got this as replacement for the defecto back when i bought Anker 2nd Gen Astro Pro2 20000mAh. Got a full refund and bought this instead. Got a full recharge of 3 time charges for my Nexus 5 from 10%-14%.Nothing much to say other than quality product and friendly customer support.
I normally don't leave reviews. If I want to buy phone accessories on amazon, my expectation on the quality is not high. However, Anker 2nd Gen Astro2 is far higher than my expectation. It is convenient that the led light is on when you move or shake the battery, telling how much juice is left. The product has a rubberized coating and is designed beautifully. I used it to recharge my HTC one. It could recharge my phone more than 2 times with the full power. Anker pays a lot of attention to the details which be told by the detailed instruction manual and a nice and small padded mesh bag.Overall, it is very well designed product at this price.
Ordered this Anker 2nd Gen Astro2 9000mAh. Worked great out of the box and already had about a half charge. I bought it for business trips and got this size to also have any coworkers covered just in case.It's a little heavy but its a battery, I don't know what I expected. Charges quickly, holds it charge, and doesn't seem to get hot which is great. Would definitely recommend.
I bought 2 batteries for me and my wife. The performance is great! My phone is charged really fast and even having to devices plugged in the charges are done in a short period of time and if you compare this unit with all other portable chargers I'm really sure that you'll buy this one. It has reliability, style, design, performance and quality. I'm not an Anker seller by the way. I'm just a satisfied customer that loves the tech gadgets and I think this company is doing a great work with all of their products.The size of the unit is very appropriate, is smaller than my previous charger the Anker Astro 3E and it feels better in the hand by the materials used to build the case.
Answer: I can tell you why I made the choice of purchasing the 2nd Gen 9000.  The new iPad Air can charge at a faster 2.4 amp and most batteries only go to 2.1.  So if there's an iPad Air in your future, this power bank will handle it.  I like that the port senses the amount of power needed for the device it's charging and adjusts accordingly.