What is the difference between medical marijuana and recreational?

Pretty much nothing except the price and availability.

The biggest difference is that Medical Patients don't pay ANY tax, not even sales tax. They also have reserved parking right next to the door and the line for our medical dispensary is often much shorter (to non-existent) compared to the Adult use line. Most products are the same and will end up on both menus at one point or another. The menus do turn over quite a bit more quickly on the Adult Use side just due to the higher volume. Also, that state dosage limit for edibles is 5mg each for Adult use but there is no limit for Medical. However, to become a patient you must first go through the required registration process to obtain your medical card while Adult use customers need only present valid, state issued ID proving they're over the age of 21.

Price, availability, potency and medical patients only pay State sales tax and are exempt from the recreational tax

As far as I am to understand, medical patients only have to pay Mass sales tax, not the 20% of recreational Marijuana. Some dispensaries also can have a wider selection of products for medical patients