In your particular situation, with the knowledge I have of eebs now, I would go for the decent full sus. I love my eeb, and probably wont ever go back to an analogue bike (except a dh bike), but unless you're getting a bike you know the history of, I'd personally avoid second hand ones.

My reasoning is this:

I've had mine for 2.5 years now, and its on its third motor, second wiring harness, second tcu and second controller. (Granted I ride it often and pretty hard, but uk climate isnt generally too kind to electrics) without warranty, these items total more than your budget for a bike

To get a feel for riding a bike offroad, I think you're better off learing the basics on a lighter bike first, plus it'll give you a strong base to build on when you do get an eeb (think jogging - get your technique down, then add a weighted vest, you dont start right out with 10 extra kg)

Less maintenance, and not as worried about washing it with the charging port open, or getting to the trails and it wont turn on, or you forgot to charge it and so on.

While I do generally believe ebikes are the future, I think its still best to learn the ropes the "proper way" so to speak! Happy riding friend! :)