Sorry I'm jumping in late... Here are my thoughts on fuel rods...
1. They are convenient. You don't need to remember to charge them over night, as soon as they are exhausted you can exchange them for another which is charged.
2. They are small. Don't take up too much room to carry.
3. Fuelrod has kiosks in airports and malls too, not just Disney Parks/Resorts.
1. You are paying for the convenience.
2. The battery capacity is usually less than 1 phone charge.
3. You WILL need to search out Kiosks in the park to exchange (because you will exhaust the battery before your day is up), potentially multiple times, which negatively impacts the convenience factor of the Fuel Rods.
4. You need more than one if you have multiple phones/family members needing them.
5. While they come with cables, you may want to carry your own to make sure it matches your device (i.e. USB-C, MicroUSB, etc) or is long enough (if you want to keep the battery in your pocket while using your phone in hand.
6. You can easily find better cost vs performance portable batteries on-line (Amazon, etc) that are higher capacity and have more ports (to charge multiple devices at one time).
That being said... My first external battery for use at WDW, long before Fuel Rods, was the Anker 2nd Gen Astro3 12800mAh External Battery. It had one port that supplies up to 2Amps and two ports that supply up to 1Amp. The total battery capacity being 12800mAh (or 12.8Ah) means we can charge an iPhone about 5 times. We used it for my phone, my wife's phone and our Nikon Coolpix S8200 camera. My wife started traveling for work, so we got another Anker 2nd Gen Astro3 12.8Ah, which now had 2A out of all 3 ports. They both still work great, even being 4+ years old.
Carrying my own, I never saw the value in the fuel rods.
Since then, we have amassed more portable electronic devices, so I purchased or otherwise acquired the following... (I've used them successfully with my various phones, tablets, cameras, and bluetooth headsets, speakers, etc. Including GS6/7/8, Note 5, Pixel, Nexus 5X, HP Elite X3, iPad Mini2, Mini3, Air, Air2 Cellular, Galaxy Tab S3, and more).
Anker PowerCore 20100 good for two devices simultaneously, including iPads. Can recharge a Galaxy S6 about 6 times, or an iPhone 6S about 7 times. While it outputs 2+ Amps per port, it doesn't support Qualcomm QC2/3 so it wont "quick charge" a Samsung Galaxy S6/Note5 or newer, but still charges them, iphones and ipads pretty quick..
Anker PowerCore+ 10050 good for single device at a time,. Qualcomm QC 2.0 support for fast charging of Samsung devices. Can recharge a Galaxy S6 about 2.5 times, or an iPhone 6s about 3 times.
Anker PowerCore Mini+ 3350mAh can charge a single iPhone from 0% to 100% once, so not ideal for park days. Can only recharge a Galaxy S6 to about 80%
RAVPower 20100mAh Portable Charger w/QC 3.0 and USB-C good for two USB-A and one USB-C device at the same time. Supports QC2/3, USBC and 2.4A USB output. Can recharge a Galaxy S6 about 6 times, or an iPhone 6s about 7 times
AUKEY 10400mAh Portable Charger with Qualcomm Quick Charge 2.0 good for a single device, be it an iPhone or Samsung phone. Supports QC2.0 for Samsung Galaxy S6 and newer. Can recharge a Galaxy S6 about 2.5 times, or an iPhone 6s about 3 times.
Another I don't have, but recommend:
Anker PowerCore+13400 can charge 2 devices simultaneously, up to 2.4a output per port, has enough capacity to charge a Galaxy S6 about 3.5 times. Or an iPhone 6 about 4.5 times. NOTE: This model supports QC2/3 for INPUT or charging itself only. It does not support QC2/3 OUTPUT to quick charge samsung phones.