IDK, as far as I know, Xanax is not habit forming if taken under a doctor's supervision and according to directions. Since it's short acting (generally affects are cleared out in about 4 hours) it generally does not give any hangover effects. If anything it sort of calms the digestive tract (my husband takes it for panic attacks, and his anxiety hits him right in the gut, the xanax totally chills that out in 45 minutes). You can take Xanax on an as needed basis, which is the best way to take it, it's a terrific drug for that use.
Paxil, being an SSRI, has the potential to impact sexual function. It's long acting, takes weeks to build to effect and can have some weird ass side effects (the suicidal ideation isn't limited to teens).
Trazadone is metabolized by the liver, a downer for anyone using other products that can impact the liver, and while not a true SSRI is sort of a chemical cousin and shares many of the side effects of SSRI. It too has to build up in the system and is meant to be taken on a steady basis and needs to be tapered off properly or there can be adverse effects.
I don't get doctors. They seem to be shying away from meds that are short acting, due to the potential of misuse. You can't really misuse a drug that takes several weeks to build to effective levels in your system. But honestly, not everyone needs long acting meds, especially with side effects that are potentially quite unpleasant.