whats good about the hosho line is you can get new CV much faster so grinding is much fun when you have a new ship. Junyo line have sexy ship structures and a little bit more space. But more people choose the hosho line because there is not much strength difference except hosho line having the advantage of fun grind.Besides at CV5-CV6 we all get the same ship anyway so it is sensible to take hosho line.

I dit a ship tree reset and actualy found that the Unryu is alot toughfer then Hiryu cause ive taken mulitple bomb hits and taken verry little damage amazingly. I guess what im trying to say is that the Unryu is a more balanceable CV compaired to the Hiryu.

If you enjoy playing mid tier CVs, go for the Junyo line. If you're planning to play the IJN CV all the way to end game, go for the Hosho line. Doesn't get anymore simpler than that.