That is a hard one to decide, both are very similar.
A2500 is easier to expand then A3000.
A3000 has Zorro III slots vs. Zorro II on A2500
A3000 has 2MB chip RAM vs 1MB on A2500 (can be expanded to 2MB for more $$$)
A3000 has VGA out standard.
A3000 can be expanded to 16MB RAM on board vs. add-on cards on A2500.
Video Toaster is nice, but only to play with and kinda useless in HD era, and if you want it anyway, you could get it later.
Actually VT runs better with 2MB chip RAM then 1MB.
Personally I would go with A3000, it a basically an improved A2500, but with less exp slots.
Before purchasing I would check if there is a battery leak on board on both computers.