I would recommend the CM450E. The only reason is that I have a 1982 CB450SC (same engine) and it runs beautifully. Personally I think that the 750 will be a bit overweight for a first bike, not really a problem when riding, but when just pushing the bike around the driveway or a parking lot you will drop it at least once in the beginning and a 400 or 450 will be easier to pick up again. The 450 will probably top out around 85 (my CB450SC will run to about 85-90 in 5th, 75-80 in 6th) and should be just about perfect for a starter bike. I could not be happier with my CB450SC Nighthawk, it's a great commuting bike and it really doesn't have any bad habits at all, a very well-behaved machine.
There are some things you need to know though. Number one, alway wear a helmet, preferably a full-face helmet. Always wear a leather motorcycle jacket. It will be a little warm sometimes, but it's a lot better than donating a pound of skin to the pavement. Always wear long heavy denim jeans (at least) and over-the-ankle boots. Also, always wear unlined motorcycle gloves too, they are nice when a bee hits your hand at 60 mph. Remember, it's very easy to get dead if you loose concentration on a motorcycle. Always ride as though every other driver were trying to kill you, never let your guard down. Give proper attention and concentration a motorcycle can be safe, but it's a demanding machine.
ZV