There is a green stevia which is the unprocessed one. Not as good as the white one in flavor. The best for your body is the green stevia. The stevia plant is green in color so I wonder what is being done to it to make it white. I would start with the green if I knew then what I know now.
Splenda is chorinated sugar, best left if you are an allergic person and also the other sweetners can be worse, try Stevia all the whole food markets and Trader Joes carry it it very sweet you dont need much can taste a little bitter but you get used to it. Cost is a bit more but you use less,and its a Natural product.
As far as I know, Diet drinks and no calorie sweetners are fine. Its mainly pure suger and carbs that hurt your suger levels.
I have been a type 1 diabetic for 1 year know and have noticed that carbs raise my suger levels more drastically than sugar does. I still stay away from sugar at all costs and try my best to stay away from foods heavy in carbs.