Truvia is made up of <1% Stevia and >99% Erythritol (a sugar alcohol mentioned several times on this thread, and supposedly the only sugar alcohol that doesn't cause digestive issues). Based on the name similarity and their branding, I had always thought Truvia was a brand of Stevia.
I was initially confused by the naming thing too.
Regarding Truvia, the stevia ingredient seems to ruin it for me. I definitely can't tolerate any stevia content. My wife thinks stevia is great. But what does she know!?
Last January I researched and tasted just about every artificial sweetener known to mankind to determine which ones I could enjoy in cider, coffee, soda pop, or anything really. Results of my review are below.
Best of the bunch, with advantages & disadvantages:
1) Xylitol -- can't barely detect any difference compared to real sugar. Has a slight "cooling effect" in the mouth in large quantities. Has a few calories, if that matters, but not fermentable by yeast as far as I know. Very expensive. LETHAL TO DOGS. I've used in cider with great success, can't taste any "chemicals".
2) Aspartame (Equal) -- the best artificial sweetener besides xylitol. Breaks down due to heat in baked goods, but seems just fine in coffee. No calories. Cheap & available. I haven't tried aspartame in a cider yet but I imagine it will be noticeable to judges.
3) Sucralose (Splenda) -- close runner-up to aspartame, but a somewhat more chemically taste. But would be better in baked goods as it won't break down. Cheap & available. Left a chemical taste in my cider that was very noticeable to BJCP judges including myself. I won't use it in cider again, but will use it in other foods if I need to cut calories or whatever.
I could not recommend ANY other artificial sweeteners available right now, including saccharin (Sweet 'n' Low), stevia, acesulfame K (Sunett), Swerve (I don't recall what's in this one), and especially monk fruit extract (OMG - disgusting!). I tasted all these, and they all suck bad in some way compared with the other 3 above. I could go into more detail, but... suffice it to say, the other ones suck real bad.
P.S. Oh yeah... I forgot Lactose! It's great, it's natural (not artificial!), but it's not very sweet. In the amounts you need to use to taste it, it can add some body to the cider or whatever you put it in. Go ahead and use lactose, but be aware that you need a lot of it, and that some people are intolerant. Most people will tolerate it just fine.
Of course, many people are also intolerant of xylitol too. I myself seem fairly tolerant of xylitol in small quantities. Depends how much you use. In a cider, you shouldn't need enough to have much effect at all. Hasn't bothered me in the slightest.