The Sunsetter (95 and newer) is a great crossover boat - it's hopefully my next boat, as my son is an avid wakeboarder. I think from 99 on, the Sunsetter LXi has the 'diamond hull' and apparently makes a difference for slalom wakes. However, if it's 'all slalom', the ps205 and echelon are better choices if you're looking for an older model.
Personally, the biggest thing to think about is the speeds you're going to be slaloming at. If you're always at 32mph and faster, I don't think any of these choices are bad. If you're pulling kids at 28 or lower, the differences start to become more obvious (Echelon would be best).
Lastly, when looking at a mid-90s boat or earlier, all-fiberglass construction is important too. But all the boats you mentioned are all-glass (the old, late 80s/early 90s sunsetters have wood stringers though).