Jeff,
First off Welcome to the Busse Forum, as you can tell I'm not Jerry, but I hope you don't mind if I take a swing at answering your questions.
The Combat line is made of INFI and has Canvas Micarta Handles. The Basic Line is made of Modified INFI (Mod-INFI) and has Respirene C Handles (rubberlike handles). The Basic line is also discontinued. See the following thread for more on this
http://www.bussecombat.com/cgi-bin/ultimatebb.cgi?ubb=get_topic&f=1&t=000112
The differences between the specific knives you have listed essentially comes down to INFI vs. Mod-INFI and Micarta vs. Respirene C handles. There are some other factors that come into play as well including blade length and overall length (OAL). The Basic 5 has 5" BL and 10" OAL whereas the BA-E has 4.5" BL and 10.25" OAL, the Basic 7 has a 7 BL and a 12" OAL and the SH-E has a 7.5 BL and 13.5 OAL, the Basic 9 and BM-E both have a 9.5 BL and 15" OAL. (some of these lengths may vary depending on where the measurement starts and stops) Someone correct me if I'm wrong on this but I believe the Combat Line has a Wider blade also, not thicker just wider. I currently don't have a Basic to compare to any combats so that is from memory.
As far as the Basics not being as tough, well that depends.
The Basic line with Mod-INFI will take anything that you can throw at it. Just ask Cliff Stamp, it took him over 2 years to break his Basic 7 and he was trying to break it.
I have never heard of a Basic that was damaged to any great extent under normal use or even abnormal use and abuse.
It really comes down to if you want the best there is, the top of the line knife, than get a Combat. If you want to save some money and have a superb knife than get a Basic. In everyday use, the Basic will live up to anything.
I hope this was helpful even if I'm not Jerry.
I really want to let Jerry keep working on knives so I can get mine
