There are too many variables.
What is your learning style? What is the teaching style? Do you have the time to devote to the course. EMT-B is not hard by any means, 3 weeks at 8 hours a day is 120 hours. That is, or is close to the requirement; I can't remember if it is 120 or 150 hours.
Most EMT courses are spead out over 6 months, because they are designed for the working person. 2 nights a week for 6 months. If you are young dumb and still living at home, or have a good savings built up, you should take the 3 week course. I would time it so your cert comes in the mail about the time your paramedic course starts.
That is where I screwed up. I should have gone on with my medic, instead I got a full time job, and no way to live for a year with little to no income and commute 60 miles a day for 6 months