Because the grass is always greener on the other side (and technically Eva is literally "greener" than CX)
And bashing too hard is always better than letting any bad thing missed so we tend to do so.
Anyway having tried transit in HKG (a slow one) and TPE (kind of) which airport isn't much to concern. Schedule wise, in July, the flight pairs with minumum layovers are
BR9-BR225 0200-0440+1 // 0740-1200 3hr layover
BR216-BR10 1510-2000 // 2355-1950 3hr layover
* CX865-CX759 0220-0645+1 // 0835-1225 1hr50min layover
* CX837-CX715 1500-1915+1 // 2025-0015+1 1hr10min layover
# CX658-CX838 0950-1405 // 1615-1330 2hr10min layover
# CX716-CX888 1805-2205 // 0030+1-2120 2hr25min layover
Which are only for reference only because we don't know when OP is travelling and not all combinations have equal pricing (aka 200CAD difference), only it seems CX has one set of schedule similar to BR and an extra set of choices (again could cost more). The offerings would be similar in economy and more down to a personal preference.
You'll likely (if not always) get a wider seat in JAL Y, and likely better food, but the cost of flights with comparably short layover seems a bit higher as well.