Some prefer one and some prefer the other, having used both.
Got two friends (actually 3 now) that hunt with an Etrac. Got two other guys I hunt with who had a Etrac and went back to the SE. So that shows you that some prefer one and some prefer the other. The Etrac makes things a bit "easier" in certain ways, like a nice luxury sports car, and in certain ways I guess you could say the Explorer is like a finicky sports car. Like comparing a Cadillac sports care to a Mustang GT. Not as easy to drive (some say) at first, but once you master it it will do some amazing things. That mastering is half the fun to some people, and so when they discover it's unique "quirks" they feel they've really built a relationship with the machine, and once that's done, to use the sports car analogy, you can out drive anybody on the road on any given day.
Some guys prefer the Explorer's VDI setup. Some say the audio on deep silver is better too. As for the Etrac, some say it has a bit more VDI on a coin at depth. So, depending on which you favor (better audio at depth on the Explorer or a tad better *conductivity* VDI at depth on a coin), you'll favor one or the other. I've owned 3 Explorer IIs and have re-searched extensively/set-up the Etrac for a few friends with the settings most of the heavy hitters seem to agree on, along with the famous Andy Sabisch excellent minimal iron discrimination pattern. Used the Etrac here and there. Prefer the Explorer myself due to the above reasons. Also, I don't care for the 12th line compression of ferrous on the Etrac myself. I seem to get much more fine detail on what a target might be in smart find with the cross hairs by what they are doing on the Explorer. Just my opinion. Both are still Minelabs and so of course great machines.
And don't think you have to get an SE. There are fans of every model of Explorer who have used them all and yet settle on one model or another for various "quirks" they like better for them. Same deal with the SE, some prefer it over the other prior models. It's all in how well you get to know the particular model and "mesh" with it IMO. Just like people you meet, some become good friends for little reasons while others you don't care for for those same little reasons. It's all in how well you get along with your machine and "connect" with it. Once that's done and you gain experience from that connection, that's when a machine goes beyond it's abilities in a sense and sets you apart from others, regardless of what machine they own.