size is relative.
I read about family of 4, full time livaboard on sub 40' monohulls all the time.
Others need 100' for part time cruising.
We wanted a 45' for livaboard. Couldn't swing the cost so we bought a 42. Plenty of room for all our stuff.
Old adage: Buy the smallest boat you can be comfortable in.
Your charter on the 38 should give you a lot to consider. Enjoy the charter but also make time to "use" the boat as if you were living aboard. Might take some imagination to just sit and think of where things would go and how you would use the boat longer term.
We went from a 26' power boat to our 42' sailboat. Really not too big a deal.