My reflex answer would be: The one that you use very little of.

It is difficult to give a general answer to your question, Steve. The reason is that research is still too spotty. What I could subscribe to is that the dose makes the poison. That goes for table sugar as much as for any artificial sweetener.

Common sense would dictate that (a) artificial sweeteners are unknown molecules to our organism, so I’d be careful in exposing the latter to the former (which I personally avoid). And (b) the industry’s efforts to develop low-calorie sugar alternatives (that are cheaper to produce than regular sugar and that can be sold at a larger profit margin due to attachable weight loss claims) will incentivize biased research of the alternatives’ health effects.

That’s why my personal strategy is to resensitize my taste buds to lower sweetness levels of the foods I consume. Living outside the US I noticed a certain sugar overkill in US recipes (my wife is running her cooking/baking experiments by me). Even half of the recommended sugar still makes the product pleasantly sweet. I suspect that this sweetening habit is indicative of desensitized sweetness receptors due to a habitual sugar overload (in processed foods).