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.