I just got back into karting after an 8 year lay off and here is what I found. If you are planning to race, there are not too many places that have Leopard only classes. The F Series in the northeast is one place and it is kinda like a Masters class with some younger drivers mixed in — all at 380lbs. Typically with high 20s / low 30s kart count.
Only race a 09MY Leopard in a mixed TAG class if you get a 10lbs weight break to an X30. Forget anything pre-09MY Leopard. All 09MY Leopards are the same You can buy a complete 09MY Leopard for $700-$1200 depending on condition
X30 are nice and very popular. You can get a used one for $1000 or so more than a Leopard — figure $1800 to $2300 for a decent responsibly fresh X30. Note all the prices I have listed are on the low side of the advertised prices what you in the Classified section of this site, but if you negotiate a little that is the real prices. I would not pay more than $800 for a topnotch Leopard and not more than $2000 for a top fresh, tuned X30
If you are not going to race, buy a Leopard. If you are going to race and there is not a good Leopard only class, buy an X30