Nope, "real time" datalogging is the only advantage of the RT. But don't let the "only" fool you. Without the real time datalogging, the only thing you will be able to do is set parameters but you won't get to see the results. I have the RT and I can't imagine doing anything without having that ability. I have my basic tunes loaded, but when I go to the track, I use the datalog feature to monitor exactly what my car is doing. With the WB o2 sensor, you can watch your AF ratio at any given point. With the RT you can see just about anything you want to see.
If you really want to take advantage of the Tweecer, get the RT and invest in a WB o2, which can be connected through the Tweecer in various ways.
Yeah, definately save for the RT. The base Tweecer is almost useless since you don't have a good way to verify what you did helped. The datalogging capability makes it really nice. Plus there is different software available to help analyze the datalogs so you can see where to focus your efforts. It takes some time to get used to but the Tweecer RT was definately the best mod I got for getting my engine to run nicely.