I took nearly 20 years of surfing and getting back into short boards i was kiddng myself that i was still only 18 years old. Well i surfed a 6'6" Super fish and found it was a year wasted as being too small i was always tired from paddling. So maybe didn't get the progression i wanted over that time.
All i can say is don't short change yourself in board size. You'll find paddling, catching waves harder therefor hurting your progression. Im supprised you find the 7'3" hard to paddle? Maybe some swimming to get your fitness will also help. Did for me.
Can't help with the boards you've put up but if your leaning one way go the easier paddler and then upgrade later

IMHO