I doubt the design of a slider made by a good firm such as Jet would be flawed imho. What was it that it couldn't do? The smaller Record has had a hard time iirc, but Martin has set his up sweet as a nut apparently. Whatever saw you buy needs setting up, and you have to be realistic when it comes to choosing the saw for the work you intend to ask it to do.
Match your saw to your expectations.
It is also about what you do a lot of as well.
Kity will not do bigger sheet work, but ideal for crosscutting smaller stock and squaring smaller panels. Bigger slider for bigger panels, but realistically you won't rip the length of a whole 8' sheet on a saw with less than a 10' slider. Yes i know you may do the odd one on your (smaller) saw, but what a struggle that is, and you'd be better of (and safer) on the floor with a circular saw and guide rail a la Matt. Pro shops need the beef of a big machine.
Just my 2d worth.