Balaos can dive much deeper than a Gato can depending on what you are running if TMO then the Balao will be able to go over 150ft deeper than a Gato no problem and that is being very conservative.Another adavantage of the Balao was that they had been redesigned somewhat from the Gato so they are able to dive much faster and they also have an improved range. I also find the Balaos lower cut conning tower to be an advantage it has a much lower profile than a Gato does. I like the Gato/Tambor for early war work but I prefer to have a Balao as soon as I can get one. And then in the last few months I will take a Tench class with its load of 28 torps and ST radar.
If you want more men you must open your game save files under SH4 inside you documents and find your subs save file the file names are tricky but click on the UPCInitial folder,activeuserplayerunits(copy and save a version somewhere else) your subs name will be at the top scroll down a bit and you will see: MaxOfficers=X MaxPettyOfficers=X change the numbers to something higher then save it. Do this when you are in the office if you want to add crew right away.Then go back to folder screen there should also be an activeuserplayerunits file under the UPCInitial folder back this one up as well and then make the same crew changes as you did before and save. Now you will be able to add the type of crew you so desire.