The Batcave is definitely the best Lego Batman set; although, you get a stupid bat-ski instead of the batmobile. You can switch the bat-ski for the batmobile that comes with the Two Face Escape set. They are build to the same scale. You can also upgrade the Penguin's submarine and Robin's jet ski with the versions that came out the following year.
It depends on how experienced you are in building. When I was 10 I could build very large LEGO sets, except for sets with ropes. If you just started building/collecting LEGO then it will be hard to build. But if you started when you was like 4 or 5 years old then I think you can build it, but maybe with some help from an adult.