The 8000 is slightly firmer, but not enough to make anyone jump up in the air and scream WOW! I had an 8000 for about a week, took it back to the dealer and said nice board, but it's not what I'm looking for. It weighed a ton, the sounds were OK, but not fantastic, and my older 5700 still sounded and felt better.
When the 740 came out, the 52-pound 5700 was still in service and I used them both in combination. Neat rig, but it took 45 minutes to set up and 8 trips tot he van just to haul in all the gear using a refrigerator dolly.
When the 2000 arrived on the scene, the advancements were astonishing. Incredible sounds, fabulous styles, great operating system, lots more memory, plus instant access to the floppy drive. This incredible machine is still being used by a lot of gigging musicians/entertainers who make a darned good living in show biz.
When the Tyros hit the streets, I was awestruck, but as much as I liked the keyboard, I really missed those onboard speakers.
Then the 3000 appeared! IMO, this is the most incredible arranger keyboard ever concieved. Huge number of fabulous styles, megavoices, incredible sampled sounds, more storage than anyone can use, lightweight, extremely versitle, and the easiest to use operating system of any keyboard I've ever owned.
I've owned lots of other brands as well. In fact, my wife says if I bring home another keyboard she's gonna' divorce me. I'm sure going to miss that woman!
One other aspect of the 8000 was the key strips, which were, and still are, a constant problem with this particular model. When the fail, and they will eventually do so, they are a real problem to replace. I've replaced them for friends and it took hours to do the job. The cost was about $80 U.S. for the strip and if the service department of the local dealer had to do it, the labor charge would have been $150 to $200 at the least.
You can replace the key pads in the 3000 in less than an hour, the strips cost $20 U.S. and the hardest part of the job is taking out the 18 case screws.
Additionaly, you'll find more 3rd party styles for Yamha than any other keyboard on the planet. However, many of those styles will not load in the 8000 without doing some major midifications. They'll all load in the 3000 and you don't have to do anything to them other than press a button and being playing.
Save your money, buy the 3000, and don't look back at acient technology--you will not regret it.
Good Luck on whatever you decide upon,