There's little doubt in my mind, based on published drug activity studies, that ethamphetamine is less toxic than methamphetamine by about 50 or 60%, and shorter acting as well, but since a larger dosage is required to achieve a similar effect, they may be about equally toxic in the long run. Both are at least partially metabolized to basic amphetamine.
Since ethamphetamine used to be a prescription drug in the United States, it probably isn't prohibitively toxic. (That is, I don't think you're dealing with another thalidomide.)
As usual, universal precautions apply. Namely, if you're going to test a new drug on yourself, start with a small dosage and work your way up. If not, I'm sure it shouldn't be hard to find a volunteer. According to wikipedia, eth was prescribed at 10 to 30 mg per day as an anorectic back in the day. A recreational dose is probably between one and two hundred milligrams.