No, triplehooked!

You aren't in trouble! The SE Pro may be a bit tougher -- it tends to run a little less "stable" than the E-Trac, meaning there will be a bit more falsing/chattering on the SE Pro for you, most likely. One key there is NOT to run your sensitivity too high, if using manual, or just run auto. You will sacrifice some depth, but still will be able to hit deep stuff -- and then when you get used to the machine a little more, you can push sensitivity up a bit -- keeping it below where it starts getting too "falsy" (Bryce recommends "26" as a good setting).
BUT -- it's only "tougher"
at first. Once you get used to it, its nuances, its sounds, and how it responds to different targets at different depths, the SE is
deadly.
Paul -- to give you a bit more complete of an answer, as you asked a few specific questions:
The USB on the E-Trac is for downloading disc. patterns from other users.
The poinpointing is different on the two; the E-Trac has a pretty nice "graphical" feature, hard to describe, that shows when you have "zeroed in" on the target, but I prefer the nuances of the SE Pro pinpointing just a bit better.
The biggest difference between the two, IMO, is that the E-Trac tries to "normalize" all "good" targets' FE values to "12." Instead of different FE values for different coins like on an Ex. II or SE/SE Pro, coins (except silver dollars) will generally ID on the FE side as "12" on an E-Trac (unless deep, or in very mineralized ground). This is a different way of looking at things, if you have prior experience with Explorers. Also, the smartfind screen is "flipped" -- where FE increases from top to bottom on the E-Trac, instead of from right to left as on the Explorers, and the CO numbers increase from left to right on the E-Trac, instead of from bottom to top on the Explorers. So, again, if you are a former Explorer user, you may find the SE Pro more to your liking (and just as capable of a hunter, IMO).
Steve