What is the difference in the level of play at a JR College DI program and a 4Yr college DI program? Are DI schools considered equally competitive in both schools or is one a higher level of competition than the other?

In general, there is a difference in the level of play within all levels.
Some D2,D3,NAIA and Juco programs play on a higher level than some D1 programs.
Much depends upon the program, so one should do their homework and determine exactly what they are looking for in a school, for academics and sports.