U14 is a wasteland of watered down teams. Its over very quickly and the better players escape to Varsity and Prep. Whats left after Thanksgiving are just young 07s and players not good enough to make varsity. Unless you're playing for Shattucks or Mount it doesnt matter.
To the Op: Since your son played BHL, E9 is fine. If your son was playing at the higher levels, I would not recommend E9. Upper kids disperse at U14 except for the BJE. Always happens. Play at the highest level he can compete at.
There is one fundamental difference 07 parents should know. League games are not important per se for a U14 NB team, getting higher MHR points are to get seeded higher in a state champ. After a couple of weeks, the higher ranked teams start to gravitate towards selective and competitive tournaments. For historically lower ranked teams with no chance to get invited to the state champ, league games may the only way to find opponents. Also Beast is not a league, bur rather a caravan attending weekend tournaments. Out of league teams are invited to their sanctioned tournament to boost their points.
From players' perspective, good U14 team is a team they can be on the first two lines with higher hockey IQ players, and be on special teams (PP/PK). Nothing is more awful than spending a season with less disciplined players at this age. Half season is too short to educate lower hockey IQ players. One more advice...be ready to contribute to a team from Week 1. The season is short and coaches quickly form impression of a player earlier in the season and put together better players in the top lines. There is no such thing as player development over six month.
You need to ask yourself this
Why are you leaving current team/ how long have you been with them for ?
Did your kid get better all the years he was there?
Where he going to play more ? Staying at same level playing top line and being part of the team or are you fine with your kid playing 3rd/4th line and not being part of a better team. Chances are he will develop more playing top 6 special teams then 3rd/4th line.
Lastly you need to look at current Beast rosters hate to say this but 85% of the team will be gone when U15 comes up. Is it worth burning a potential bridge for a goofy year of hockey. Yeah I chased the dream followed the U14 talk and my kid got cut once U15 came around because now these top dogs really get players from all over the country who are attending prep schools.
Beat advice is to stick at current team develop for high school season and if your good enough they will come back to you at the levels they really care about U15 and up.