I haven't really read into it much recently, but from what I recall, they're all probably fine in reasonable amounts. Most studies feed them to rats in quantities that are absurdly unrealistic for a human to consume. If, at the end of the day, one helps you feel better and more satiated than another, avoid real sugar, and keep a healthy weight, I'd go with that one.
That being said, I'd imagine both stevia and monk fruit are probably better for you wholistically than the more artificial ones like saccharin or sucralose. I have only ever tried stevia, didn't really find it sweet enough for me. Had a weird taste. It also had something else in it though, I think erithritol. So I don't know.
Also, I think the key to cutting back on sugar, for most people, is the hidden sugars in foods. If you have one tsp of sugar in a cup of tea, but you enjoy that cup of tea more than you would with a substitute, might be worth it.