I'm a classic gizmo freak. I almost never leave the house without my smartwatch, e-reader, and phone, and I often add my iPad mini and wireless flash drive* to that list. I also attend a few conventions every year, and I usually add a camera, an old Palm PDA, and a couple of iPods to my kit for those. All of which is to say that I know what it's like to need a recharge on the go...
First, to be honest, I can pretty much scratch the watch and e-reader off of my list. I juice 'em up before I leave on the trip, and they're good for the duration. Similarly, the camera (and my speakers, if I bring those) uses rechargeable AA batteries, and I can usually just toss some of those in the bag and call it good. That leaves the iStuff, flash drive, phone, and PDA as charging concerns. All together, that's five different connectors: USB, micro-USB, 30-pin, Lightning, and Palm.
I still view my FuelTank Duo as my "big" portable battery. It's got some great features, like two charging ports, an easy-to-read charge-remaining meter, and a decent capacity for its generation (4300mAh) - but it's fairly bulky (by 2013 standards) and requires its own custom adapters, which are major minuses. For instance, they still don't have a Lightning tip...but at least they work with the six-port charging station that I can set up in my hotel room.
So, with that in mind, I've mostly switched to a much smaller Power Bank unit. It's about the size of a lipstick tube and is rated at 3300 mAh, so it packs a lot more punch than the Duo for the size and weight. It's only got one charging port, but it's a standard USB port and I've got a nifty 3-in-1 squid connector that turns that into an Apple 30-pin, Lightning, and micro-USB connector...which takes care of most of my needs. (It uses a micro-USB input to recharge, so the squid does double duty.) It lacks a charge meter, but at least it has an on/off button and a charge/discharge light. Plus, it easily fits in my pocket.
When I went to Dragon Con this year, I packed both battery packs with me...and I never needed to break out the Duo. Part of it was simply not using my electronics that much, but the Power Bank just satisfied my needs. I may pick up another one if I see a good deal on it - ideally with a higher capacity or at least a different color - but so far, it looks like I could drop the Duo from my gear without blinking. The only use I had for it was to loan it to a friend in case she needed it...and she didn't. Yes, this means I'll have to pack the Palm cable to replace the Duo's adapter, but that's no big deal.
So, my recommendation: get a couple of small yet potent external batteries. The Power Bank/squid combo is just about perfect, in my opinion - and if they changed the design to make the power button into a deliberate switch (harder to toggle by accident), that'd be even better.
* The "wireless flash drive" is exactly that: a combination thumb drive and WiFi hotspot - a LAN on a lanyard, if you will. Very handy for swapping files or streaming media on the go, although you do have to use a computer or the Android/iOS app to add files to it. Even then, you can't rename, delete, or move files around on it via WiFi; you have to access it as a USB drive for that. Decent security feature, I guess...