I have both, the Classic is I don't know how old, bought used in a box of fish junk at a garage sale. I also have 2 Eccos, bought used with used fish tanks. I also have Pro and Pro2. Only Pro2 was bought new.
Classic; good flow rate, even the old one with no basket is pretty easy to clean and prime. Silent. Frequently lasts for 10 to 30 years with care.
Ecco; much less flow rate, I can see why it has no spray bar. Creates more of a surface disturbance than I'd like in a planted tank for that reason. Got to be careful when disconnecting for cleaning, must close valves in correct order, then turn off power, in order to not screw up the lid opening mechanism. I run them with substrat media plus pads, not just the pads as sold. A lot more parts than the Classic, more stuff to break or lose. One of the ones I have is missing a seal between baskets and the gear for lid opening was not working well (OK now with correct instructions being followed) for a while I had to use a screw driver to get it opened.
Pro 2; great flow rate, even more parts to keep track of. Thermofilter cords make it harder to clean filter, can't just unplug and carry to the sink.
Summary; if I were getting another filter (and I may replace the Fluval 303 before long) I'd get a Classic for the best value for the money.