There are so many out there, and I'm a bit lost
I wonder what are the differences between them, and what should I be looking for
(I drive a 2001 Chevy Astro if that matters)

It depends. Are you a professional like myself? Or just want to keep one handy for that "special" day.
For the latter, I recommend Harbor Freight. Just shop price.

Thanks for the quick reply
I just want it for "emergencies", I am not a pro, but also don't drive much, so the battery dies every few months
But I shopping for price I bought a cheap jack for emergencies, and last week it broke under the weight of my car, so I had to throw it away, and call my insurance company's roadside assistance

I recommend that you buy an old-fashioned 6 amp. Battery charger with an ammeter (e.g. Schauer), remove the battery, and charge it until the ammeter doesn't cut back anymore--usually between 1 and 2 amps. With jumpers, I've seen people fry their ECMs--due to voltage spikes. It doesn't take much. My dad bought an expensive charger/jumper several years ago--it's temperamental and won't even charge the battery sometimes. I'm always suggesting that he just use his old charger.

Here's an example of what I'm suggesting:

http://compare.ebay.com/like/2206216...=263602_309572