The chart shows 18650's at 3.6v so I'm assuming that the ones advertised at 3.7v are another manufacturer rebranded as Panasonic? Will they be any better or am I over thinking this?
You're over thinking this. There are no 3.6V Panasonic 18650B's and 3.7V Panasonic 18650B's. In both cases you're talking about the
same 18650B (=type) from Panasonic (=manufacturer). Which according to Panasonic itself, has a 3.6V
nominal voltage, with
typical capacity of 3350 mAh. The latter measured using the charge/discharge conditions found in the datasheet.
Anything other than that is just a different way to describe the same thing (aka marketing bla bla). Note that the 3.6V is just a kind of
average along a charge/discharge curve, roughly halfway between peak voltage (~4.2V) and lowest that is considered empty/safe end voltage (usually ~3.0V). 3.7V is just a slightly value for what's regarded as "average", but doesn't change that charge/discharge curve, or the cell's properties.
Other than that, the only relevant thing about any seller offering Panasonic 18650B, is whether they're
genuine Panasonic 18650B, or fake. A cell that says "Panasonic" and "18650B" on the label, but has a different cell under the wrapper, is simply a fake. In which case it could be
anything, including sand-filled with a $0.10, 200 mAh pouch cell inside.
Note that these 18650B's are bare cells (unprotected) only. Protected versions of these are "Panasonic 18650B inside, protection circuit + wrapper by a 3rd party". Which come with different circuits & different colored wrappers, and may or may not have the advertized cell inside...
I hate ordering something online when there is the possibility that for a little extra I can have something better.
In that case pay attention to
who/where you're buying from, at least as much as reading the advert.
"Better" depends on what equipment you use a cell in, and a variety of other factors besides a single mAh number (build quality / safety / how many years or cycles they might last / high-current capability, protected or bare cell, etc, etc).
For example one of my last 18650 buys, I faced the choice between a (discounted) 6 Euro, 2900 mAh cell made by Samsung, or buying a Panny 18650B (which IIRC was ~10 Euro at the time). Since most of my lights aren't high-draw, useful capacity should be close to the specced numbers for me. Which made me go for the Samsung here: roughly 85% of the highest available capacity, for almost half the price. More than enough capacity for my uses, higher price/performance ratio, and thus
(for me, in that particular case) the "better" option. What's "better" for you simply depends on your uses, budget and priorities.
