Court Supervision is available once in a lifetime in Illinois for DUI sentencing purposes. And indeed for DUI offenders who are eligible, DuPage Judges will typically impose court supervision rather than a conviction because of the downstream consequences of a DUI conviction (upon conviction for DUI the Secretary of State shall revoke the Defendant's driver's license). Court Supervision is, by definition not a conviction.
The problem is that some jurisdictions don't recognize the Illinois regime for Court Supervision. Most notable among these jurisdictions is Canada. Canada considers DUI to be a "serious offense" and can be a basis for Canada to bar entry into the country.
Some DuPage DUI defense attorneys overlook this fact and will not address the issue properly before plea bargaining. Thus setting their client up for a big surprise down the road when he or she has to go to Toronto or somewhere else in the Great White North for business or pleasure.
If you regularly travel to Canada and have a DuPage DUI case pending make sure to discuss this with your attorney before you agree to Court Supervision. If you've had supervision for a DUI within the last five years and are expecting to travel to Canada, you should contact the Canadian consulate.