Do penalties differ between the two, or is it just a matter of the substance taken?
Same thing. Some states believe that driving while "intoxicated" suggests to juries that you have to be stumbling drunk.
Speeding / Traffic Ticket Lawyer
Different states have different names for a "drunk driving" charge. In Washington it's Driving Under the Influence (DUI). Oregon calls it Driving Under the Influence of an Intoxicant (DUII). Other states call it Driving While Intoxicated (DWI) or Operating While Intoxicated (OWI), etc... All generally the same thing, but the laws in every state are a little different.
Criminal Defense Attorney
The penalties are the same. The substance does not matter either. DUI refers to the .08 standard. DWI refers to the "Officer's opinion" standard for intoxication. You can be under .08 and still "intoxicated" in the Officer's opinion and subject to being charged.
At your service,