Valid points for and against both classes, and I would find myself having the same dilemma. If I honestly couldn't decide based on the outline of the class alone, I would consider other criteria (if known); Does one class have an "easier to tote" supply list?, Is one class offered at a preferred day or time of day?, Are both classes the same amount of total hours? Does one class have a smaller "maximum" number of students?
If none of the above answers are known, or don't make any difference to you, I would choose the second class for the reasons you stated - arrive early and try to sit in the front of the class. Even if there are more newbies there that shouldn't be there, hopefully the class will be designed so that your own skill level will allow you to continue on your own after the technique has been demonstrated.