You’re welcome, I’m glad to help!
The standard LED Maglights are not even in the same league as these. The Mag XL50 is a small pocket light with 100-200 lumens max. It is bright to the average person, however I once gifted one of those and felt bad about it because the output was so weak compared to what I’m used to in a light that size.
I assume the 3D mag you have is the standard version (168 lumens) not the ML300 (625 lumens)? Compared to the standard 168 lumen 3D mag light these lights will “completely blow it out of the water”
The 625 lumen ML300 series 3D mag appears to be quite an improvement over their previous designs, however these 18650 powered lights will easily have as much if not more output and you’re comparing a pocketable size light that pretty much fits in your hand to one that is a nearly foot long and about one pound in weight, and eats batteries that you will have to keep replacing. So based on size alone there’s no comparison.
Since your asking about the side by side configuration I assume you are interested in the Small Sun ZY-T08 that I linked. That one runs the batteries in parallel, not series. Parallel configuration is safer than series it cuts the current drain in half, it also provides the option to run a single battery at the same brightness. The ZY-T08 is said to be an excellent thrower.
Here is a link to a nice review on the Small Sun: https://budgetlightforum.com/t/-/12179
With any Li-ion flashlight you should have a voltmeter/multi-meter to check battery voltages, especially for multi cell lights. Even a cheap one will do for checking battery voltages (or the free one from Harbor Freight Tools w/coupon with any purchase) For single cell lights you could get away without one if the light has a built in low voltage indication feature.
The other posts with the links provided above answer the safety concerns for a 2 cell series flashlight (batteries usually end to end) and multi battery lights.
For the 2 cell lights consider they are larger in size, and the battery run time for the single cell lights are pretty good, especially on the lower levels. Whats nice about the X6 is its compact size, so its more portable if you decide to take it along on a walk, hike, outing or trip, instead of it being a home use only light.
Compared to a 3D mag light you will be surprised how it outputs so much better for its size. With 3 brightness levels you can lower the output when needed to conserve battery power for extend run time. Just get 2 of the Samsung 26F batteries and you can keep the spare handy if needed.
The Samsung 26F cells from where I linked reportedly are good, but here is another place to buy them that was linked in another reply as well (USA based and the owner is forum member here) Although they’re a few dollars more than the ones from the Chinese shop you can be more certain you are getting the high-quality Seiko protection circuit: http://www.mtnelectronics.com/index.php?route=product/product&path=59_88&product_id=599