I now have five-to-seven years of player data for Canadian Junior A leagues, so it's now possible to generate equivalencies for each league. I ran the data for British Columbia (BCHL), Alberta (AJHL), Saskatchewan (SJHL), Manitoba (MJHL), Ontario (OPJHL), Quebec (QJAHL) and the Maritimes (MJAHL).

The Quebec and Maritimes leagues did not send a significant number of players to the NCAA, and few players went from the SJHL to Major Junior. The Manitoba league was more likely to send players to other Junior A league than to have them step up to a higher-level of hockey.

Here are the equivalencies normalized to a player age of 18:

Junior A to NCAA	EQUIV	Mean Age	N
*USHL	0.66	19.41	384
AJHL	0.39	18.38	91
BCHL	0.34	18.34	190
OPJHL	0.32	18.33	94
SJHL	0.31	18.37	42

A huge drop from the USHL to the Junior A leagues - but not a huge difference among the Canadian leagues. The AJHL seems to have a higher level of play.

Junior A to Major Junior	EQUIV	Mean Age	N
AJHL	0.61	17.43	48
BCHL	0.57	18.70	34
QJAHL	0.51	18.51	30
MJAHL	0.47	17.62	31
OPJHL	0.44	18.44	217

Less of a difference this time, but again the AJHL is on top.

Major Junior to Junior A	EQUIV	Mean Age	N
BCHL	0.33	18.37	33
SJHL	0.27	19.17	29
AJHL	0.22	18.80	43
QJAHL	0.21	18.71	85
MJAHL	0.20	19.23	19
OPJHL	0.17	18.20	71

Note that the equivalency is in this table is actually for Junior A to Major Junior so that we can compare the relative performance of players stepping up a level of hockey versus those stepping down. Junior A leagues appear substantially less difficult for players coming from Major Junior than they did to players going in the other direction.

Overall, assuming that the level of play is identical in all three Canadian major Leagues (which has been shown elsewhere on this site), then the BCHL and AJHL appear to have the highest level of play of all the Junior A leagues.