They're both sweeteners, I'm wondering what the difference is
They're both sweeteners. TFA Sweetener is a 10% sucralose (Splenda) solution, which can form crystals in low temperature (warm it to re-dissolve), and can gunk your coils if used at higher percentages. Ethyl Maltol produces a cotton candy flavor at higher percentages, but can sweeten and "round out" recipes at the lower end. If used for sweetness above 1.5%, it can really mute the other flavors.
I sometimes use these in combination (generally 0.5% each), but I find that many--even most--recipes don't require additional sweetening for me.
They're both sweeteners. TFA Sweetener is a 10% sucralose (Splenda) solution, ...
So what do you all think is best?
No. Sucralose is Not Splenda.
If I had to add sweetness, I'd lean towards EM if the recipe's flavors had some harsh edges, but would favor sucralose-based Sweetener otherwise. I've often done half-and-half with them both, because of some trivia stuck in my brain about the synergy of combining different artificial sweeteners. But I think it's best not to use any, since both PG and VG taste sweet, and many common flavoring ingredients will impart sweetness too. Nowadays, my first mix test is done without any sweetener.
Right you are, and in fact there are now some Splenda products that don't contain any sucralose at all. ChelsB, I didn't mean to imply that you should use Splenda-brand sweetener to mix your own e-liquid sweetener; you shouldn't. I just wanted to give you a handle on what sucralose was and where you may have encountered it before, in case you hadn't run across the name before.