If it is that HS in Dutchess there is a big difference in talent between the two varsity teams. My son’s HS played both teams last year (some games are scheduled by the Section that you must play), and depending upon your desire to be competitive you may not like the “B” team.
And for what it’s worth, there are some schools in this Section that have Varsity B teams due to parental pressure more than enrollment numbers. My son’s HS has about 1600 kids and has a “B” team in a couple of sports. They also have JV teams. Fortunately Baseball wasn’t one of them.