|[ http://www.haltech.com/wp-content/uploads/2017/03/0317_ECUchart_SinglePage.pdf ]
The 2500 has:
1. 2 more outputs
2. While the input quantity is the same, 4 can be used either as digital or analog whereas on the 2000, they are fixed as digital.
3. Supports drive by wire throttle. (Not that this matters unless you are looking to convert).
4. Long term knock learning
5. Supports variable cam control for up to 4 cams versus 2 (this doesn't matter as our cam control is a simple on /off with no feedback, whereas modern engine cam control allows for control of the exact phasing).
6. Long term ignition learning (4D).
7. 2mb 40 channel data logging at 200Hz vs. 1mb 20 channel at 20Hz.
8. Supports OEM Canbus (doesn't matter in our application).
9. Supports 4D tuning tables with a resolution of 32x32x8 vs. 3D with a resolution of 32x32.
10. Multi-level engine protection vs. single level
11. 6 stages of nitrous control versus 1.
12. 4D boost control vs. 3D.
More info here: [ http://www.haltech.com/new-product-elite-1000-and-elite-2000/ ]