Another factor of transferring is getting a year older when sitting out due to transfer rules. If that year is spent getting bigger faster stronger that can be great. But nobody is getting scouted sitting on the bench.
This thread speaks to why I often recommend late bloomers (especially those not interested in the high academic route) to go JUCO instead of D3. Take a couple years to develop as much as you can before the game of Baseball tells you if you are a D1, D2, or D3 talent at the age of 20, not 18...