The AE is the very best for the money. You need a laptop or PDA to use it. What makes the AE so special is it will run many special tests like the injector buzz test, it will even run a test for your wipers!!
If you are just looking for a good code reader and clearer I suggest the SCT2 unit. Both will do live data logging although the AE will data log more parameters. It all depends on what your needs are.