I have AE. Best money I've spent on the truck. I already had a laptop, so I didn't have that expense, but any old USB laptop will work fine; one with Windows XP is better than Win98, and Win95 doesn't play well with USB. I would only buy the USB AE, since the license is tied to the dongle instead of the computer. ...and it's been quite a while since laptops came with a serial port. Just make sure your laptop battery is good, since the instructions say not to use the AE tool with a power inverter connected to the truck. ...something about ground loops.
I would not want the PDA version. I have a 12" screen at 1024 x 768 (yes, it's old), and wish it were bigger so I could see more parameters at once.
It has time set function, as well as TDC learn. You can turn off individual cylinders to check for imbalance. There are a lot more features, but It's late and I'm too tired to think.
Just get it; you won't regret it. I don't know how you'd ever diagnose problems without it.